Immediate and high performance flexible packaging applications using thermal lamination and new primer technology

ABSTRACT

A process for preparing a flexible packaging material (6) by laminating at a temperature greater or equal to 50° C. a printed substrate coated with a primer (4) comprising poly(acrylic acid) and/or poly(methacrylic acid) with another substrate coated with a thermal active material (2), to prepare a high performance flexible packaging multilayer material (6) showing improved shelf-life, without requiring curing stage of intermediate layers.

All manner of consumer goods, in particular food products, are packagedusing thin films or sheets of flexible packaging material, with imagessuch as corporate branding, or product information printed onto thefilm. The flexible packaging material serves to protect the productfrom, for example, moisture, oxidation or pathogens, while alsoproviding information to the user regarding the nature and origin of theproduct contained therein.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a schematic of a process for producing a flexible packagingmaterial in accordance with the present disclosure.

DETAILED DESCRIPTION

Before the present disclosure is disclosed and described, it is to beunderstood that this disclosure is not limited to the particular processsteps and materials disclosed herein because such process steps andmaterials may vary somewhat. It is also to be understood that theterminology used herein is used for the purpose of describing particularembodiments. The terms are not intended to be limiting because the scopeis intended to be limited by the appended claims and equivalentsthereof.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

As used herein, “carrier fluid”, “carrier liquid,” “carrier,” or“carrier vehicle” refers to the fluid in which pigment particles,colorant, charge directors and other additives can be dispersed to forma liquid electrostatic composition or a liquid electrophotographiccomposition. The carrier liquids may include a mixture of a variety ofdifferent agents, such as surfactants, co-solvents, viscosity modifiers,and/or other possible ingredients.

As used herein, “electrostatic ink composition” or “liquidelectrophotographic composition” generally refers to an ink compositionthat is typically suitable for use in an electrostatic printing process,sometimes termed an electrophotographic printing process. It maycomprise pigment particles, which may comprise a thermoplastic resin.

As used herein, “pigment” generally includes pigment colorants, magneticparticles, aluminas, silicas, and/or other ceramics or organo-metallics,whether or not such particulates impart color. Thus, though the presentdescription primarily exemplifies the use of pigment colorants, the term“pigment” can be used more generally to describe not only pigmentcolorants, but other pigments such as organometallics, ferrites,ceramics, etc.

As used herein, “copolymer” refers to a polymer that is polymerized fromat least two monomers.

As used herein, “lamination bond strength” refers to the force (perlength) required to delaminate a laminated material, and is expressed inunits of Newton/inch, or N/in. The lamination bond strength can bemeasured according to standard techniques, in particular ASTMF0904-98R08. Unless otherwise stated, the lamination bond strength of aflexible packaging material described herein refers the strength todelaminate the material at the interface between a thermally activatablelaminating material and either of the two materials to which thethermally activatable laminating material has bonded.

As used herein, “melt flow rate” generally refers to the extrusion rateof a resin through an orifice of defined dimensions at a specifiedtemperature and load, usually reported as temperature/load, e.g. 190°C./2.16 kg. Flow rates can be used to differentiate grades or provide ameasure of degradation of a material as a result of molding. In thepresent disclosure, “melt flow rate” is measured per ASTM D1238-04cStandard Test Method for Melt Flow Rates of Thermoplastics by ExtrusionPlastometer, as known in the art. If a melt flow rate of a particularpolymer is specified, unless otherwise stated, it is the melt flow ratefor that polymer alone, in the absence of any of the other components ofthe electrostatic ink composition.

As used herein, “acidity,” “acid number,” or “acid value” refers to themass of potassium hydroxide (KOH) in milligrams that neutralizes onegram of a substance. The acidity of a polymer can be measured accordingto standard techniques, for example as described in ASTM D1386. If theacidity of a particular polymer is specified, unless otherwise stated,it is the acidity for that polymer alone, in the absence of any of theother components of the liquid toner composition.

As used herein, “melt viscosity” generally refers to the ratio of shearstress to shear rate at a given shear stress or shear rate. Testing isgenerally performed using a capillary rheometer. A plastic charge isheated in the rheometer barrel and is forced through a die with aplunger. The plunger is pushed either by a constant force or at constantrate depending on the equipment. Measurements are taken once the systemhas reached steady-state operation. One method used is measuringBrookfield viscosity at 140° C., units are mPa·s or cPoise, as known inthe art. Alternatively, the melt viscosity can be measured using arheometer, e.g. a commercially available AR-2000 Rheometer from ThermalAnalysis Instruments, using the geometry of: 25 mm steel plate-standardsteel parallel plate, and finding the plate over plate rheometryisotherm at 120° C., 0.01 hz shear rate. If the melt viscosity of aparticular polymer is specified, unless otherwise stated, it is the meltviscosity for that polymer alone, in the absence of any of the othercomponents of the electrostatic ink composition.

A certain monomer may be described herein as constituting a certainweight percentage of a polymer. This indicates that the repeating unitsformed from the said monomer in the polymer constitute said weightpercentage of the polymer.

If a standard test is mentioned herein, unless otherwise stated, theversion of the test to be referred to is the most recent at the time offiling this patent application.

As used herein, “electrostatic printing” or “electrophotographicprinting” generally refers to the process that provides an image that istransferred from a photo imaging substrate either directly or indirectlyvia an intermediate transfer member to a print substrate. As such, theimage is not substantially absorbed into the photo imaging substrate onwhich it is applied. Additionally, “electrophotographic printers” or“electrostatic printers” generally refer to those printers capable ofperforming electrophotographic printing or electrostatic printing, asdescribed above. “Liquid electrophotographic printing” is a specifictype of electrophotographic printing where a liquid composition isemployed in the electrophotographic process rather than a powder toner.An electrostatic printing process may involve subjecting theelectrostatic composition to an electric field, e.g. an electric fieldhaving a field gradient of 50-400 V/μm, or more, in some examples600-900 V/μm, or more. As used herein, the term “about” is used toprovide flexibility to a numerical range endpoint by providing that agiven value may be a little above or a little below the endpoint toallow for variation in test methods or apparatus. The degree offlexibility of this term can be dictated by the particular variable aswould be understood in the art.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not just the numerical valuesexplicitly recited as the limits of the range, but also to include allthe individual numerical values or sub-ranges encompassed within thatrange as if each numerical value and sub-range is explicitly recited. Asan illustration, a numerical range of “about 1 wt % to about 5 wt %”should be interpreted to include not just the explicitly recited valuesof about 1 wt % to about 5 wt %, but also include individual values andsubranges within the indicated range. Thus, included in this numericalrange are individual values such as 2, 3.5, and 4 and sub-ranges such asfrom 1-3, from 2-4, and from 3-5, etc. This same principle applies toranges reciting a single numerical value. Furthermore, such aninterpretation should apply regardless of the breadth of the range orthe characteristics being described.

As used herein, wt % values are to be taken as referring to aweight-for-weight (w/w) percentage of solids in the ink composition, andnot including the weight of any carrier fluid present.

Unless otherwise stated, any feature described herein can be combinedwith any aspect or any other feature described herein.

In an aspect there is provided a process for preparing a flexiblepackaging material comprising:

-   -   providing a first flexible substrate coated with a primer        comprising poly(acrylic acid) and/or poly(methacrylic acid);    -   printing a liquid electrophotographic printing ink composition        onto the surface of the first flexible substrate;    -   extruding a thermally activatable laminating material onto a        surface of a second flexible substrate; and    -   contacting, under conditions of temperature of at least 50° C.,        the surface of the second flexible substrate on which the        thermally activatable laminating material is deposited with the        surface of the first flexible substrate printed with the liquid        electrophotographic printing ink composition.

In another aspect there is provided a flexible packaging materialcomprising:

-   -   a first flexible substrate coated with a primer comprising        poly(acrylic acid) and/or poly(methacrylic acid);    -   a printed liquid electrophotographic printing ink composition        disposed on a surface of the first flexible substrate; and    -   a second flexible substrate on which a thermally activatable        laminating material is deposited, the surface of the second        flexible substrate on which a thermally activatable laminating        material is deposited being thermally laminated to the surface        of the first flexible substrate printed with the ink        composition.

In another aspect there is provided a flexible package comprising aflexible packaging material comprising:

a first flexible substrate coated with a primer comprising poly(acrylicacid) and/or poly(methacrylic acid);

-   -   a printed liquid electrophotographic printing ink composition        disposed on a surface of the first flexible substrate; and    -   a second flexible substrate on which a thermally activatable        laminating material is deposited, the surface of the second        flexible substrate on which a thermally activatable laminating        material is deposited being thermally laminated to the surface        of the first flexible substrate printed with the ink        composition.

Much research has been carried out in recent years to try to developlaminated flexible packaging materials comprising a functional (barrier)substrate laminated to a second substrate comprising a printed image orinformation. Some existing laminated flexible packaging materials havebeen found to be unsuitable for use in particular circumstances, such asstorage of particular items (e.g. food, detergent, chemical), packagestorage conditions (e.g. humid conditions which may be found inparticular geographical locations, or in refrigerators or freezers), andhigh performance flexible packaging in which packages are required towithstand, for example, processes for extending the shelf life or foodsuch as pasteurization and retort. Printed images or information on someexisting laminated flexible packaging materials have been found todiscolour on heating, for example on heat sealing of a package orlamination bond strength of some existing laminated flexible packagesmay be found to decrease on heating causing defects between the layersduring thermal processes such as pasteurization and retort. Thesolutions proposed today consist on applying an adhesive coating on theprinted substrate and laminating the coated printed substrate with asecond substrate such as film, foil, paper or laminate. Adhesivecoatings require a prolonged period of curing (over seven days) toovercome regulatory issues and to allow adhesive coatings to reachmaximum strength before moving to the next converting processes. Thus,there is a lag time between a flexible packaging material being producedand the material being ready for packaging food. When used with digitalprinting processes, conventional laminating technologies negate theadvantage of short turnaround on the printing process due to longpost-printing processes/wait times.

The present inventors have found that examples of the process asdescribed herein avoid or at least mitigate at least one of thedifficulties described above. They have found that examples of theprocess are more successful than previous processes in that thelamination and bonding is immediate such that no cure time is required(zero cure time). The process described can be implemented in-line witha conventional electrostatic printing process, thus further streamliningthe process for producing flexible packaging materials.

Flexible Packaging Material

In one example, a flexible packaging material is described. The flexiblepackaging material may be produced by any of the methods describedherein. Each component of the flexible packaging material will bediscussed in the sections which follow.

In one example, the flexible packaging material comprises a laminatestructure with sufficient bond strength to avoid delamination of thelayers, in particular delamination at the interface between the secondflexible substrate on which a thermally activatable laminating materialis laminated and the surface of the first flexible substrate printedwith the ink composition. In one example, the lamination bond strengthis measured directly after the flexible packaging material has cooled toroom temperature following lamination, without having been subjected toany curing or rest period following lamination and cooling. In oneexample, the lamination bond strength is measured according to ASTMF0904-98R08. In one example, the flexible packaging material has alamination bond strength of at least about 1.0 N/inch, for example atleast about 1.5 N/inch, for example at least about 2.0 N/inch, forexample at least about 2.5 N/inch, for example at least about 3.0N/inch, for example at least about 4.0 N/inch, for example at leastabout 5.0 N/inch, for example at least about 6.0 N/inch, for example atleast about 7.0 N/inch, for example at least about 8.0 N/inch, forexample at least about 9.0 N/inch, for example about 10.0 N/inch, asmeasured by ASTM F0904-98R08.

First Flexible Substrate

The flexible substrate, to which the primer comprising poly(acrylicacid) and/or poly(methacrylic acid) is coated and to which a liquidelectrophotographic printing ink composition is to be printed may be anymaterial suitable for use in a printing process and suitable for use ina flexible packaging material. Since the first flexible substrate formsthe outermost layer of the final, laminated flexible packaging materialas prepared in the methods described herein, in one example the flexiblesubstrate is transparent in order that the printed image or informationis visible to the consumer.

In one example, the first flexible substrate comprises a film of apolymer, for example a thermoplastic polymer. In one example, the firstflexible substrate comprises a film of biaxially oriented polypropylene(BOPP), polyethylene terephthalate (PET), polypropylene (PP) andoriented polyamide (OPA). Other suitable polymers will be known in theart and the examples provided above should be seen as non-limitingexamples only.

In one example, the first flexible substrate comprises a thin film of apolymer, wherein the film is less than 100 μm in thickness, for exampleless than 90 μm in thickness, less than 80 μm in thickness, less than 70μm in thickness, less than 60 μm in thickness, less than 50 μm inthickness, less than 40 μm in thickness, less than 30 μm in thickness,less than 20 μm in thickness, less than 15 μm in thickness. In oneexample, the film of polymer is about 10 μm in thickness.

In one example, the first flexible substrate comprises a thin film of apolymer, wherein the film is greater than 10 μm in thickness, forexample greater than 15 μm in thickness, greater than 20 μm inthickness, greater than 30 μm in thickness, greater than 40 μm inthickness, greater than 50 μm in thickness, greater than 60 μm inthickness, greater than 70 μm in thickness, greater than 80 μm inthickness, greater than 90 μm in thickness. In one example, the film ofpolymer is about 100 μm in thickness.

The first flexible substrate has a surface on which a primer comprisingpoly(acrylic acid) and/or poly(methacrylic acid) is disposed, the inkcomposition being then disposed on a surface of the first flexiblesubstrate.

In some examples, the primer comprises poly(acrylic acid).

In some examples, the primer may comprise a copolyester. The copolyestermay be formed when modifications are made to polyesters, which arecombinations of diacids and diols. In some examples, the copolyester isformed by introducing other diacids, such as isophthalic acid, or otherdiols, such as cyclohexane dimethanol to the polyester. The materialbecomes a copolyester due to its comonomer content. In some examples,the comonomer content is of 1-50 wt % of the copolyester.

In some examples, the primer comprising poly(acrylic acid) and/orpoly(methacrylic acid) on the surface of the flexible print substratesurface is provided in an amount such that the coat weight of the primercomprising poly(acrylic acid) and/or poly(methacrylic acid) on the printsubstrate is at least 0.01 g/m², in some examples at least 0.05 g/m², insome examples at least 0.1 g/m², in some examples at least 0.15 g/m², insome examples about 0.18 g/m². In some examples the primer comprisingpoly(acrylic acid) and/or poly(methacrylic acid) is provided in anamount such that the coat weight of the primer comprising poly(acrylicacid) and/or poly(methacrylic acid) on the print substrate is up toabout 0.2 g/m², in some examples up to about 0.5 g/m², in some examplesup to about 1 g/m², in some examples up to about 1.5 g/m².

In some examples, the first flexible substrate coated with a primercomprising poly(acrylic acid) and/or poly(methacrylic acid) is aSarafil® product (available from Polyplex). In some examples, the firstflexible substrate coated with a primer comprising poly(acrylic acid)and/or poly(methacrylic acid) is a Sarafil® DP product of Polyplex inwhich the first flexible substrate is a biaxyally oriented polyethyleneterephthalate (BOPET) material, such as Sarafil® DP100-1G. In someexamples, the first flexible substrate coated with a primer comprisingpoly(acrylic acid) and/or poly(methacrylic acid) is a Sarafil® DBproduct of Polyplex in which the first flexible substrate is a biaxyallyoriented polypropylene (BOPP) material, such as Sarafil® DB100-1GO.

In some examples, the first flexible substrate is printed with an imageor information on a first surface of the first flexible substrate. Theimage or information may be reverse printed onto the first surface ofthe substrate with a second surface of the first flexible substrateforming the outermost surface of the flexible packaging material and theprinted image or information appearing the right way round when viewedthrough the second surface of the first flexible substrate. In this way,the printed image or information is embedded within the multi-layerstructure of the flexible packaging material and not on the outermostsurface, and thus protected from damage.

Ink Composition

The ink composition printed on the first flexible substrate coated withthe primer comprising poly(acrylic acid) and/or poly(methacrylic acid)described herein is a Liquid Electrophotographic Printing.

(also referred to herein as a LEP composition) useful in the methodsdescribed herein to form flexible packaging materials also describedgenerally comprises a colorant or pigment, a polymer resin and a carrierfluid or liquid. The LEP composition may further comprise one or moreadditives such as charge directors, charge adjuvants, surfactants,viscosity modifiers, emulsifiers and the like. In some examples, the LEPcomposition may not contain any pigment, or comprise substantially zeropigment and thus be a pigment-free composition, useful in providing aparticular transparent gloss or sheen to a printed substrate.

In some examples, after printing, the LEP composition printed on thefirst flexible substrate described herein may comprise a reduced amountof carrier liquid compared with the LEP printing composition beforeprinting. In some examples, the LEP composition printed on the firstflexible substrate coated with the primer comprising poly(acrylic acid)and/or poly(methacrylic acid) described herein, may be substantiallyfree from carrier liquid. Substantially free from carrier liquid mayindicate that the ink printed on the first flexible substrate containsless than 5 wt % carrier liquid, in some examples, less than 2 wt %carrier liquid, in some examples less than 1 wt % carrier liquid, insome examples less than 0.5 wt % carrier liquid. In some examples, theLEP composition printed on the first flexible substrate is free fromcarrier liquid.

Each of these components of an electrostatic ink composition will bedescribed separately in the subsections which follow.

Colorant

The LEP composition may comprise a colorant. The colorant may be a dyeor pigment. The colorant can be any colorant compatible with the liquidcarrier and useful for electrophotographic printing. For example, thecolorant may be present as pigment particles, or may comprise a resin(in addition to the polymers described herein) and a pigment. The resinsand pigments can be any of those commonly used as known in the art. Insome examples, the colorant is selected from a cyan pigment, a magentapigment, a yellow pigment and a black pigment. For example, pigments byHoechst including Permanent Yellow DHG, Permanent Yellow GR, PermanentYellow G, Permanent Yellow NCG-71, Permanent Yellow GG, Hansa Yellow RA,Hansa Brilliant Yellow 5GX-02, Hansa Yellow X, NOVAPERM® YELLOW HR,NOVAPERM® YELLOW FGL, Hansa Brilliant Yellow 10GX, Permanent YellowG3R-01, HOSTAPERM® YELLOW H4G, HOSTAPERM® YELLOW H3G, HOSTAPERM® ORANGEGR, HOSTAPERM® SCARLET GO, Permanent Rubine F6B; pigments by SunChemical including L74-1357 Yellow, L75-1331 Yellow, L75-2337 Yellow;pigments by Heubach including DALAMAR® YELLOW YT-858-D; pigments byCiba-Geigy including CROMOPHTHAL® YELLOW 3 G, CROMOPHTHAL® YELLOW GR,CROMOPHTHAL® YELLOW 8 G, IRGAZINE® YELLOW 5GT, IRGALITE® RUBINE 4BL,MONASTRAL® MAGENTA, MONASTRAL® SCARLET, MONASTRAL® VIOLET, MONASTRAL®RED; pigments by BASF including LUMOGEN® LIGHT YELLOW, PALIOGEN® ORANGE,HELIOGEN® BLUE L 690 IF, HELIOGEN® BLUE TBD 7010, HELIOGEN® BLUE K 7090,HELIOGEN® BLUE L 710 IF, HELIOGEN® BLUE L 6470, HELIOGEN® GREEN K 8683,HELIOGEN® GREEN L 9140; pigments by Mobay including QUINDO® MAGENTA,INDOFAST® BRILLIANT SCARLET, QUINDO® RED 6700, QUINDO® RED 6713,INDOFAST® VIOLET; pigments by Cabot including Maroon B STERLING® NSBLACK, STERLING® NSX 76, MOGUL® L; pigments by DuPont including TIPURE®R-101; and pigments by Paul Uhlich including UHLICH® BK 8200. Where thepigment is a white pigment particle, the pigment particle may beselected from the group consisting of TiO₂, calcium carbonate, zincoxide, and mixtures thereof. In some examples the white pigment particlemay comprise an alumina-TiO₂ pigment.

In some examples, the colorant or pigment particles may have a medianparticle size or d₅₀ of less than 20 μm, for example less than 15 μm,for example less than 10 μm, for example less than 5 μm, for exampleless than 4 μm, for example less than 3 μm, for example less than 2 μm,for example less than 1 μm, for example less than 0.9 μm, for exampleless than 08 μm, for example less than 0.7 μm, for example less than 0.6μm, for example less than 0.5 μm. Unless otherwise stated, the particlesize of the colorant or pigment particle and the resin coated pigmentparticle is determined using laser diffraction on a Malvern Mastersizer2000 according to the standard procedure as described in the operatingmanual.

The colorant or pigment particle may be present in the LEP compositionin an amount of from 10 wt % to 80 wt % of the total amount of resin andpigment, in some examples 15 wt % to 80 wt %, in some examples 15 wt %to 60 wt %, in some examples 15 wt % to 50 wt %, in some examples 15 wt% to 40 wt %, in some examples 15 wt % to 30 wt % of the total amount ofresin and colorant. In some examples, the colorant or pigment particlemay be present in the LEP composition in an amount of at least 50 wt %of the total amount of resin and colorant or pigment, for example atleast 55 wt % of the total amount of resin and colorant or pigment.

Polymer Resin

The LEP composition comprises a polymer resin which may comprise acopolymer of an alkylene monomer and a monomer selected from acrylicacid and methacrylic acid. The polymer resin may be referred to as athermopastic polymer. A thermoplastic polymer is sometimes referred toas a thermoplastic resin. In some examples, the polymer resin maycomprise one or more of ethylene or propylene acrylic acid copolymers;ethylene or propylene methacrylic acid copolymers; ethylene vinylacetate copolymers; copolymers of ethylene or propylene (e.g. 80 wt % to99.9 wt %), and alkyl (e.g. C₁ to C₅) ester of methacrylic or acrylicacid (e.g. 0.1 wt % to 20 wt %); copolymers of ethylene (e.g. 80 wt % to99.9 wt %), acrylic or methacrylic acid (e.g. 0.1 wt % to 20.0 wt %) andalkyl (e.g. C₁ to C₅) ester of methacrylic or acrylic acid (e.g. 0.1 wt% to 20 wt %); copolymers of ethylene or propylene (e.g. 70 wt % to 99.9wt %) and maleic anhydride (e.g. 0.1 wt % to 30 wt %); polyethylene;polystyrene; isotactic polypropylene (crystalline); copolymers ofethylene ethyl acrylate; polyesters; polyvinyl toluene; polyamides;styrene/butadiene co-polymers; epoxy resins; acrylic resins (e.g.co-polymer of acrylic or methacrylic acid and at least one alkyl esterof acrylic or methacrylic acid wherein alkyl may have from 1 to about 20carbon atoms, such as methyl methacrylate (e.g. 50% to 90%)/methacrylicacid (e.g. 0 wt % to 20 wt %)/ethylhexylacrylate (e.g. 10 wt % to 50 wt%); ethylene-acrylate terpolymers: ethylene-acrylic esters-maleicanhydride (MAH) or glycidyl methacrylate (GMA) terpolymers;ethylene-acrylic acid ionomers and combinations thereof.

The polymer resin may comprise a polymer having acidic side groups.Examples of the polymer having acidic side groups will now be described.The polymer having acidic side groups may have an acidity of 50 mg KOH/gor more, in some examples an acidity of 60 mg KOH/g or more, in someexamples an acidity of 70 mg KOH/g or more, in some examples an acidityof 80 mg KOH/g or more, in some examples an acidity of 90 mg KOH/g ormore, in some examples an acidity of 100 mg KOH/g or more, in someexamples an acidity of 105 mg KOH/g or more, in some examples 110 mgKOH/g or more, in some examples 115 mg KOH/g or more. The polymer resinhaving acidic side groups may have an acidity of 200 mg KOH/g or less,in some examples 190 mg or less, in some examples 180 mg or less, insome examples 130 mg KOH/g or less, in some examples 120 mg KOH/g orless. Acidity of a polymer, as measured in mg KOH/g can be measuredusing standard procedures known in the art, for example using theprocedure described in ASTM D1386.

The polymer resin may comprise a polymer having acidic side groups, thathas a melt flow rate of less than about 70 g/10 minutes, in someexamples about 60 g/10 minutes or less, in some examples about 50 g/10minutes or less, in some examples about 40 g/10 minutes or less, in someexamples 30 g/10 minutes or less, in some examples 20 g/10 minutes orless, in some examples 10 g/10 minutes or less. In some examples, allpolymers having acidic side groups and/or ester groups in the particleseach individually have a melt flow rate of less than 90 g/10 minutes, 80g/10 minutes or less, in some examples 80 g/10 minutes or less, in someexamples 70 g/10 minutes or less, in some examples 70 g/10 minutes orless, in some examples 60 g/10 minutes or less.

The polymer having acidic side groups can have a melt flow rate of about10 g/10 minutes to about 120 g/10 minutes, in some examples about 10g/10 minutes to about 70 g/10 minutes, in some examples about 10 g/10minutes to 40 g/10 minutes, in some examples 20 g/10 minutes to 30 g/10minutes. The polymer having acidic side groups can have a melt flow rateof, in some examples, about 50 g/10 minutes to about 120 g/10 minutes,in some examples 60 g/10 minutes to about 100 g/10 minutes. The meltflow rate can be measured using standard procedures known in the art,for example as described in ASTM D1238.

The acidic side groups may be in free acid form or may be in the form ofan anion and associated with one or more counterions, typically metalcounterions, e.g. a metal selected from the alkali metals, such aslithium, sodium and potassium, alkali earth metals, such as magnesium orcalcium, and transition metals, such as zinc. The polymer having acidicsides groups can be selected from resins such as copolymers of ethyleneand an ethylenically unsaturated acid of either acrylic acid ormethacrylic acid; and ionomers thereof, such as methacrylic acid andethylene-acrylic or methacrylic acid copolymers which are at leastpartially neutralized with metal ions (e.g. Zn, Na, Li) such as Surlyn®ionomers. The polymer comprising acidic side groups can be a copolymerof ethylene and an ethylenically unsaturated acid of either acrylic ormethacrylic acid, where the ethylenically unsaturated acid of eitheracrylic or methacrylic acid constitute from 5 wt % to about 25 wt % ofthe copolymer, in some examples from 10 wt % to about 20 wt % of thecopolymer.

The polymer resin may comprise two different polymers having acidic sidegroups. The two polymers having acidic side groups may have differentacidities, which may fall within the ranges mentioned above. The resinmay comprise a first polymer having acidic side groups that has anacidity of from 10 mg KOH/g to 110 mg KOH/g, in some examples 20 mgKOH/g to 110 mg KOH/g, in some examples 30 mg KOH/g to 110 mg KOH/g, insome examples 50 mg KOH/g to 110 mg KOH/g, and a second polymer havingacidic side groups that has an acidity of 110 mg KOH/g to 130 mg KOH/g.

The polymer resin may comprise two different polymers having acidic sidegroups: a first polymer having acidic side groups that has a melt flowrate of about 10 g/10 minutes to about 50 g/10 minutes and an acidity offrom 10 mg KOH/g to 110 mg KOH/g, in some examples 20 mg KOH/g to 110 mgKOH/g, in some examples 30 mg KOH/g to 110 mg KOH/g, in some examples 50mg KOH/g to 110 mg KOH/g, and a second polymer having acidic side groupsthat has a melt flow rate of about 50 g/10 minutes to about 120 g/10minutes and an acidity of 110 mg KOH/g to 130 mg KOH/g. The first andsecond polymers may be absent of ester groups.

The ratio of the first polymer having acidic side groups to the secondpolymer having acidic side groups can be from about 10:1 to about 2:1.The ratio can be from about 6:1 to about 3:1, in some examples about4:1.

The polymer resin may comprise a polymer having a melt viscosity of15000 poise or less, in some examples a melt viscosity of 10000 poise orless, in some examples 1000 poise or less, in some examples 100 poise orless, in some examples 50 poise or less, in some examples 10 poise orless; said polymer may be a polymer having acidic side groups asdescribed herein. The polymer resin may comprise a first polymer havinga melt viscosity of 15000 poise or more, in some examples 20000 poise ormore, in some examples 50000 poise or more, in some examples 70000 poiseor more; and in some examples, the resin may comprise a second polymerhaving a melt viscosity less than the first polymer, in some examples amelt viscosity of 15000 poise or less, in some examples a melt viscosityof 10000 poise or less, in some examples 1000 poise or less, in someexamples 100 poise or less, in some examples 50 poise or less, in someexamples 10 poise or less. The polymer resin may comprise a firstpolymer having a melt viscosity of more than 60000 poise, in someexamples from 60000 poise to 100000 poise, in some examples from 65000poise to 85000 poise; a second polymer having a melt viscosity of from15000 poise to 40000 poise, in some examples 20000 poise to 30000 poise,and a third polymer having a melt viscosity of 15000 poise or less, insome examples a melt viscosity of 10000 poise or less, in some examples1000 poise or less, in some examples 100 poise or less, in some examples50 poise or less, in some examples 10 poise or less; an example of thefirst polymer is Nucrel® 960 (from DuPont), and example of the secondpolymer is Nucrel® 699 (from DuPont), and an example of the thirdpolymer is A-C® 5120 or A-C® 5180 (from Honeywell). The first, secondand third polymers may be polymers having acidic side groups asdescribed herein. The melt viscosity can be measured using a rheometer,e.g. a commercially available AR-2000 Rheometer from Thermal AnalysisInstruments, using the geometry of: 25 mm steel plate-standard steelparallel plate, and finding the plate over plate rheometry isotherm at120° C., 0.01 Hz shear rate.

If the polymer resin comprises a single type of polymer, the polymer(excluding any other components of the electrophotographic inkcomposition) may have a melt viscosity of 6000 poise or more, in someexamples a melt viscosity of 8000 poise or more, in some examples a meltviscosity of 10000 poise or more, in some examples a melt viscosity of12000 poise or more. If the resin comprises a plurality of polymers allthe polymers of the polymer resin may together form a mixture (excludingany other components of the electrophotographic ink composition) thathas a melt viscosity of 6000 poise or more, in some examples a meltviscosity of 8000 poise or more, in some examples a melt viscosity of10000 poise or more, in some examples a melt viscosity of 12000 poise ormore. Melt viscosity can be measured using standard techniques. The meltviscosity can be measured using a rheometer, e.g. a commerciallyavailable AR-2000 Rheometer from Thermal Analysis Instruments, using thegeometry of: 25 mm steel plate-standard steel parallel plate, andfinding the plate over plate rheometry isotherm at 120° C., 0.01 Hzshear rate.

The polymer resin may comprise two different polymers having acidic sidegroups that are selected from copolymers of ethylene and anethylenically unsaturated acid of either acrylic acid or methacrylicacid; or ionomers thereof, such as methacrylic acid and ethylene-acrylicor methacrylic acid copolymers which are at least partially neutralizedwith metal ions (e.g. Zn, Na, Li) such as Surlyn® ionomers. The polymerresin may comprise (i) a first polymer that is a copolymer of ethyleneand an ethylenically unsaturated acid of either acrylic acid andmethacrylic acid, wherein the ethylenically unsaturated acid of eitheracrylic or methacrylic acid constitutes from 8 wt % to about 16 wt % ofthe copolymer, in some examples 10 wt % to 16 wt % of the copolymer; and(ii) a second polymer that is a copolymer of ethylene and anethylenically unsaturated acid of either acrylic acid and methacrylicacid, wherein the ethylenically unsaturated acid of either acrylic ormethacrylic acid constitutes from 12 wt % to about 30 wt % of thecopolymer, in some examples from 14 wt % to about 20 wt % of thecopolymer, in some examples from 16 wt % to about 20 wt % of thecopolymer in some examples from 17 wt % to 19 wt % of the copolymer.

The polymer resin may comprise a polymer having acidic side groups, asdescribed above (which may be free of ester side groups), and a polymerhaving ester side groups. The polymer having ester side groups may be athermoplastic polymer. The polymer having ester side groups may furthercomprise acidic side groups. The polymer having ester side groups may bea copolymer of a monomer having ester side groups and a monomer havingacidic side groups. The polymer may be a copolymer of a monomer havingester side groups, a monomer having acidic side groups, and a monomerabsent of any acidic and ester side groups. The monomer having esterside groups may be a monomer selected from esterified acrylic acid oresterified methacrylic acid. The monomer having acidic side groups maybe a monomer selected from acrylic or methacrylic acid. The monomerabsent of any acidic and ester side groups may be an alkylene monomer,including, for example, ethylene or propylene. The esterified acrylicacid or esterified methacrylic acid may, respectively, be an alkyl esterof acrylic acid or an alkyl ester of methacrylic acid. The alkyl groupin the alkyl ester of acrylic or methacrylic acid may be an alkyl grouphaving 1 to 30 carbons, in some examples 1 to 20 carbons, in someexamples 1 to 10 carbons; in some examples selected from methyl, ethyl,iso-propyl, n-propyl, t-butyl, iso-butyl, n-butyl and pentyl.

The polymer having ester side groups may be a copolymer of a firstmonomer having ester side groups, a second monomer having acidic sidegroups and a third monomer which is an alkylene monomer absent of anyacidic and ester side groups. The polymer having ester side groups maybe a copolymer of (i) a first monomer having ester side groups selectedfrom esterified acrylic acid or esterified methacrylic acid, in someexamples an alkyl ester of acrylic or methacrylic acid, (ii) a secondmonomer having acidic side groups selected from acrylic or methacrylicacid and (iii) a third monomer which is an alkylene monomer selectedfrom ethylene and propylene. The first monomer may constitute 1% to 50%by weight of the copolymer, in some examples 5% to 40% by weight, insome examples 5% to 20% by weight of the copolymer, in some examples 5%to 15% by weight of the copolymer. The second monomer may constitute 1%to 50% by weight of the copolymer, in some examples 5% to 40% by weightof the copolymer, in some examples 5% to 20% by weight of theco-polymer, in some examples 5% to 15% by weight of the copolymer. Thefirst monomer can constitute 5% to 40% by weight of the copolymer, thesecond monomer constitutes 5% to 40% by weight of the copolymer, andwith the third monomer constituting the remaining weight of thecopolymer. In some examples, the first monomer constitutes 5% to 15% byweight of the copolymer, the second monomer constitutes 5% to 15% byweight of the copolymer, with the third monomer constituting theremaining weight of the copolymer. In some examples, the first monomerconstitutes 8% to 12% by weight of the copolymer, the second monomerconstitutes 8% to 12% by weight of the copolymer, with the third monomerconstituting the remaining weight of the copolymer. In some examples,the first monomer constitutes about 10% by weight of the copolymer, thesecond monomer constitutes about 10% by weight of the copolymer, andwith the third monomer constituting the remaining weight of thecopolymer. The polymer may be selected from the Bynel® class of monomer,including Bynel 2022 and Bynel 2002, which are available from DuPont.

The polymer having ester side groups may constitute 1% or more by weightof the total amount of the resin polymers, e.g. thermoplastic resinpolymers, in the liquid electrophotographic ink composition printed onthe print substrate, e.g. the total amount of the polymer or polymershaving acidic side groups and polymer having ester side groups. Thepolymer having ester side groups may constitute 5% or more by weight ofthe total amount of the resin polymers, e.g. thermoplastic polymers, insome examples 8% or more by weight of the total amount of the resinpolymers, e.g. thermoplastic polymers, in some examples 10% or more byweight of the total amount of the resin polymers, e.g. thermoplasticpolymers, in some examples 15% or more by weight of the total amount ofthe resin polymers, e.g. thermoplastic polymers, in some examples 20% ormore by weight of the total amount of the resin polymers, e.g.thermoplastic polymers, in some examples 25% or more by weight of thetotal amount of the resin polymers, e.g. thermoplastic polymers, in someexamples 30% or more by weight of the total amount of the resinpolymers, e.g. thermoplastic polymers, in some examples 35% or more byweight of the total amount of the resin polymers, e.g. thermoplasticpolymers, in the LEP composition printed on the print substrate. Thepolymer having ester side groups may constitute from 5% to 50% by weightof the total amount of the resin polymers, e.g. thermoplastic resinpolymers, in the LEP composition printed on the print substrate, in someexamples 10% to 40% by weight of the total amount of the resin polymers,e.g. thermoplastic polymers, in the LEP composition printed on the printsubstrate, in some examples 5% to 30% by weight of the total amount ofthe resin polymers, e.g. thermoplastic polymers, in the LEP compositionprinted on the print substrate, in some examples 5% to 15% by weight ofthe total amount of the resin polymers, e.g. thermoplastic polymers, inthe LEP composition printed on the print substrate, in some examples 15%to 30% by weight of the total amount of the resin polymers, e.g.thermoplastic polymers, in the LEP composition printed on the printsubstrate.

The polymer having ester side groups may have an acidity of 50 mg KOH/gor more, in some examples an acidity of 60 mg KOH/g or more, in someexamples an acidity of 70 mg KOH/g or more, in some examples an acidityof 80 mg KOH/g or more. The polymer having ester side groups may have anacidity of 100 mg KOH/g or less, in some examples 90 mg KOH/g or less.The polymer having ester side groups may have an acidity of 60 mg KOH/gto 90 mg KOH/g, in some examples 70 mg KOH/g to 80 mg KOH/g.

The polymer having ester side groups may have a melt flow rate of about10 g/10 minutes to about 120 g/10 minutes, in some examples about 10g/10 minutes to about 50 g/10 minutes, in some examples about 20 g/10minutes to about 40 g/10 minutes, in some examples about 25 g/10 minutesto about 35 g/10 minutes.

The polymer, polymers, copolymer or copolymers of the thermoplasticresin can in some examples be selected from the Nucrel® family of toners(e.g. Nucrel® 403, Nucrel® 407, Nucrel® 609HS, Nucrel® 908HS, Nucrel®1202HC, Nucrel® 30707, Nucrel® 1214, Nucrel® 903, Nucrel® 3990, Nucrel®910, Nucrel® 925, Nucrel® 699, Nucrel® 599, Nucrel® 960, Nucrel® RX 76,Nucrel® 2806, Bynel® 2002, Bynel® 2014, Bynel® 2020 and Bynel® 2022,(sold by DuPont)), the A-C® family of toners (e.g. A-C® 5120, A-C® 5180,A-C® 540, A-C® 580 (sold by Honeywell)), the AClyn® family of toners(e.g. AClyn® 201, AClyn® 246, AClyn® 285 and AClyn® 295), and theLotader® family of toners (e.g. Lotader® 2210, Lotader® 3430 andLotader® 8200 (sold by Arkema)).

The polymer resin can constitute about 5 to 90%, in some examples about50 to 80%, by weight of the solids of the LEP composition printed ontothe surface of the first flexible substrate. The resin can constituteabout 60 to 95%, in some examples about 70 to 95%, by weight of thesolids of the LEP composition printed onto the surface of the firstflexible substrate.

Carrier Liquid

In some examples, the LEP composition comprises polymer resin coatedpigment particles, or resin particles, which are formed in and/ordispersed in a carrier fluid or carrier liquid. Before application tothe print substrate in the electrostatic printing process, the inkcomposition may be an electrostatic ink composition, which may be in dryform, for example in the form of flowable pigment particles coated withthe thermoplastic resin. Alternatively, before application to the printsubstrate in the electrostatic printing process, the electrostatic inkcomposition may be in liquid form; and may comprise a carrier liquid inwhich is suspended pigment particles coated with the thermoplasticresin.

Generally, the carrier liquid acts as a reaction solvent in preparingthe coated pigment particles, and can also act as a dispersing mediumfor the other components in the resulting electrostatic ink composition.In some examples, the carrier liquid is a liquid which does not dissolvethe polymer resin at room temperature. In some examples, the carrierliquid is a liquid which dissolves the polymer resin at elevatedtemperatures. For example, the polymer resin may be soluble in thecarrier liquid when heated to a temperature of at least 80° C., forexample 90° C., for example 100° C., for example 110° C., for example120° C. For example, the carrier liquid can comprise or be ahydrocarbon, silicone oil, vegetable oil, etc. The carrier liquid caninclude, but is not limited to, an insulating, non-polar, non-aqueousliquid that can be used as a medium for toner particles. The carrierliquid can include compounds that have a resistivity in excess of about10⁹ ohm-cm. The carrier liquid may have a dielectric constant belowabout 5, in some examples below about 3. The carrier liquid can includehydrocarbons. The hydrocarbon can include an aliphatic hydrocarbon, anisomerized aliphatic hydrocarbon, branched chain aliphatic hydrocarbons,aromatic hydrocarbons, and combinations thereof. Examples of the carrierliquids include aliphatic hydrocarbons, isoparaffinic compounds,paraffinic compounds, dearomatized hydrocarbon compounds, and the like.In particular, the carrier liquids can include Isopar-G™, Isopar-H™,Isopar-L™, Isopar-M™, Isopar-K™, Isopar-V™, Norpar 12™, Norpar 13™,Norpar 15™, Exxol D40™, Exxol D80™, Exxol D100™, Exxol D130™, and ExxolD140™ (each sold by EXXON CORPORATION); Teclen N-16™, Teclen N-20™,Teclen N-22™, Nisseki Naphthesol L™, Nisseki Naphthesol M™, NissekiNaphthesol H™, #0 Solvent L™, #0 Solvent M™, #0 Solvent H™, NissekiIsosol 300™, Nisseki Isosol 400™, AF-4™, AF-5™, AF-6™ and AF-7™ (eachsold by NIPPON OIL CORPORATION); IP Solvent 1620™ and IP Solvent 2028™(each sold by IDEMITSU PETROCHEMICAL CO., LTD.); Amsco OMS™ and Amsco460™ (each sold by AMERICAN MINERAL SPIRITS CORP.); and Electron,Positron, New II, Purogen HF (100% synthetic terpenes) (sold byECOLINK).

Before printing, the carrier liquid can constitute about 20% to 99.5% byweight of the electrostatic ink composition, in some examples 50% to99.5% by weight of the electrostatic ink composition. Before printing,the carrier liquid may constitute about 40 to 90% by weight of theelectrostatic ink composition. Before printing, the carrier liquid mayconstitute about 60% to 80% by weight of the electrostatic inkcomposition. Before printing, the carrier liquid may constitute about90% to 99.5% by weight of the electrostatic ink composition, in someexamples 95% to 99% by weight of the electrostatic ink composition.

The electrostatic ink composition, when printed onto the surface of thefirst flexible substrate, may be substantially free from carrier liquid.In an electrostatic printing process and/or afterwards, the carrierliquid may be removed, e.g. by an electrophoresis processes duringprinting and/or evaporation, such that substantially just solids aretransferred to the print substrate. Substantially free from carrierliquid may indicate that the ink printed onto the surface of the firstflexible substrate contains less than 5 wt % carrier liquid, in someexamples, less than 2 wt % carrier liquid, in some examples less than 1wt % carrier liquid, in some examples less than 0.5 wt % carrier liquid.In some examples, the ink printed onto the surface of the first flexiblesubstrate is free from carrier liquid.

Charge Director and Charge Adjuvant

The ink composition printed onto the surface of the first flexiblesubstrate can comprise a charge director. A charge director can be addedto an electrostatic composition to impart a charge of a desired polarityand/or maintain sufficient electrostatic charge on the particles of anelectrostatic ink composition. The charge director may comprise ioniccompounds, including, for example, metal salts of fatty acids, metalsalts of sulfo-succinates, metal salts of oxyphosphates, metal salts ofalkyl-benzenesulfonic acid, metal salts of aromatic carboxylic acids orsulfonic acids, as well as zwitterionic and non-ionic compounds, such aspolyoxyethylated alkylamines, lecithin, polyvinylpyrrolidone, organicacid esters of polyvalent alcohols, etc. The charge director can beselected from oil-soluble petroleum sulfonates (e.g. neutral CalciumPetronate™, neutral Barium Petronate™, and basic Barium Petronate™),polybutylene succinimides (e.g. OLOA™ 1200 and Amoco 575), and glyceridesalts (e.g. sodium salts of phosphated mono- and diglycerides withunsaturated and saturated acid substituents), sulfonic acid saltsincluding, for example, barium, sodium, calcium, and aluminium salts ofsulfonic acid. The sulfonic acids may include, for example, alkylsulfonic acids, aryl sulfonic acids, and sulfonic acids of alkylsuccinates (e.g. see WO 2007/130069). The charge director can impart anegative charge or a positive charge on the resin-containing particlesof an electrostatic ink composition.

The charge director can comprise a sulfosuccinate moiety of the generalformula: [R_(a)—O—C(O)CH₂CH(SO₃ ⁻)C(O)—O—R_(b)], where each of R_(a) andR_(b) is an alkyl group. In some examples, the charge director comprisesnanoparticles of a simple salt and a sulfosuccinate salt of the generalformula MA_(n), wherein M is a metal, n is the valence of M, and A is anion of the general formula [R_(a)—O—C(O)CH₂CH(SO₃ ⁻)C(O)—O—R_(b)], whereeach of R_(a) and R_(b) is an alkyl group, or other charge directors asfound in WO 2007/130069, which is incorporation herein by reference inits entirety. As described in WO 2007/130069, the sulfosuccinate salt ofthe general formula MA_(n) is an example of a micelle forming salt. Thecharge director may be substantially free or free of an acid of thegeneral formula HA, where A is as described above. The charge directormay comprise micelles of said sulfosuccinate salt enclosing at leastsome of the nanoparticles. The charge director may comprise at leastsome nanoparticles having a size of 200 nm or less, in some examples 2nm or more. As described in WO 2007/130069, simple salts are salts thatdo not form micelles by themselves, although they may form a core formicelles with a micelle forming salt. The ions constructing the simplesalts are all hydrophilic. The simple salt may comprise a cationselected from Mg, Ca, Ba, NH₄, tert-butyl ammonium, Li⁺, and Al³⁺, orfrom any subgroup thereof. The simple salt may comprise an anionselected from SO₄ ²⁻, PO³⁻, NO³⁻, HPO₄ ²⁻, CO₃ ²⁻, acetate,trifluoroacetate (TFA), Cl⁻, Bf, F, ClO₄ ⁻, and TiO₃ ⁴⁻, or from anysub-group thereof. The simple salt may be selected from CaCO₃, Ba₂TiO₃,Al₂(SO₄), Al(NO₃)₃, Ca₃(PO₄)₂, BaSO₄, BaHPO₄, Ba₂(PO₄)₃, CaSO₄,(NH₄)₂CO₃, (NH₄)₂SO₄, NH₄OAc, tert-butyl ammonium bromide, NH₄NO₃,LiTFA, Al₂(SO₄)₃, LiClO₄ and LiBF₄, or any sub-group thereof. The chargedirector may further comprise basic barium petronate (BBP).

In the formula [R_(a)—O—C(O)CH₂CH(SO₃ ⁻)C(O)—O—R_(b)], in some examples,each of R_(a) and R_(b) is an aliphatic alkyl group. In some examples,each of R_(a) and R_(b) independently is a C₆₋₂₅ alkyl. In someexamples, said aliphatic alkyl group is linear. In some examples, saidaliphatic alkyl group is branched. In some examples, said aliphaticalkyl group includes a linear chain of more than 6 carbon atoms. In someexamples, R_(a) and R_(b) are the same. In some examples, at least oneof R_(a) and R_(b) is C₁₃H₂₇. In some examples, M is Na, K, Cs, Ca, orBa. The formula [R_(a)—O—C(O)CH₂CH(SO₃ ⁻)C(O)—O—R_(b)] and/or theformula MA_(n) may be as defined in any part of WO 2007/130069.

The charge director may comprise (i) soya lecithin, (ii) a bariumsulfonate salt, such as basic barium petronate (BPP), and (iii) anisopropyl amine sulfonate salt. Basic barium petronate is a bariumsulfonate salt of a 21-26 hydrocarbon alkyl, and can be obtained, forexample, from Chemtura. An example isopropyl amine sulphonate salt isdodecyl benzene sulfonic acid isopropyl amine, which is available fromCroda.

In an electrostatic ink composition, the charge director can constituteabout 0.001% to 20%, in some examples 0.01 to 20% by weight, in someexamples 0.01 to 10% by weight, in some examples 0.01 to 1% by weight ofthe solids of the electrostatic ink composition printed onto the surfaceof the first flexible substrate. The charge director can constituteabout 0.001 to 0.15% by weight of the solids of the liquidelectrophotographic ink composition printed onto the surface of thefirst flexible substrate, in some examples 0.001 to 0.15%, in someexamples 0.001 to 0.02% by weight of the solids of the liquidelectrophotographic ink composition printed onto the surface of thefirst flexible substrate. In some examples, the charge director impartsa negative charge on the electrostatic ink composition. The particleconductivity may range from 50 to 500 pmho/cm, in some examples from200-350 pmho/cm.

The ink composition printed onto the surface of the first flexiblesubstrate can comprise a charge adjuvant. A charge adjuvant may bepresent with a charge director, and may be different to the chargedirector, and act to increase and/or stabilise the charge on particles,e.g. resin-containing particles, of an electrostatic composition. Thecharge adjuvant can include, for example, barium petronate, calciumpetronate, Co salts of naphthenic acid, Ca salts of naphthenic acid, Cusalts of naphthenic acid, Mn salts of naphthenic acid, Ni salts ofnaphthenic acid, Zn salts of naphthenic acid, Fe salts of naphthenicacid, Ba salts of stearic acid, Co salts of stearic acid, Pb salts ofstearic acid, Zn salts of stearic acid, Al salts of stearic acid, Cusalts of stearic acid, Fe salts of stearic acid, metal carboxylates(e.g. Al tristearate, Al octanoate, Li heptanoate, Fe stearate, Fedistearate, Ba stearate, Cr stearate, Mg octanoate, Ca stearate, Fenaphthenate, Zn naphthenate, Mn heptanoate, Zn heptanoate, Ba octanoate,Al octanoate, Co octanoate, Mn octanoate, and Zn octanoate), Colineolates, Mn lineolates, Pb lineolates, Zn lineolates, Ca oleates, Cooleates, Zn palmirate, Ca resinates, Co resinates, Mn resinates, Pbresinates, Zn resinates, AB diblock copolymers of 2-ethylhexylmethacrylate-co-methacrylic acid calcium, and ammonium salts, copolymersof an alkyl acrylamidoglycolate alkyl ether (e.g. methylacrylamidoglycolate methyl ether-co-vinyl acetate), and hydroxybis(3,5-di-tert-butyl salicylic) aluminate monohydrate. In someexamples, the charge adjuvant is aluminium di and/or tristearate and/oraluminium di and/or tripalmitate.

The charge adjuvant can constitute about 0.1 to 5% by weight of thesolids of the liquid electrophotographic ink composition printed ontothe surface of the first flexible substrate. The charge adjuvant canconstitute about 0.5 to 4% by weight of the solids of the liquidelectrophotographic ink composition printed onto the surface of thefirst flexible substrate. The charge adjuvant can constitute about 1 to3% by weight of the solids of the liquid electrophotographic inkcomposition printed onto the surface of the first flexible substrate.

Other Additives

The electrophotographic ink composition may include an additive or aplurality of additives. The additive or plurality of additives may beadded at any stage of the method. The additive or plurality of additivesmay be selected from a wax, a surfactant, biocides, organic solvents,viscosity modifiers, materials for pH adjustment, sequestering agents,preservatives, compatibility additives, emulsifiers and the like. Thewax may be an incompatible wax. As used herein, “incompatible wax” mayrefer to a wax that is incompatible with the resin. Specifically, thewax phase separates from the resin phase upon the cooling of the resinfused mixture on a print substrate during and after the transfer of theink film to the print substrate, e.g. from an intermediate transfermember, which may be a heated blanket.

Second Flexible Substrate

The second flexible substrate may also be referred to as a functionalsubstrate or simply a base layer. The base layer of the flexiblepackaging material may be the innermost layer of the flexible packagingmaterial in use, and may thus be in contact with the packaged goods. Insome examples, the base layer is referred to as a functional substrateand is functional in the sense that it provides a barrier function toprotect the packaged goods. The base layer or functional substrate mayserve as a barrier to any external influence that could damage orotherwise reduce the quality of the packaged goods, in particular food,by preventing ingress of, for example, moisture, oxygen, other oxidantsand pathogens such as viruses and bacteria.

In some examples, the second flexible substrate comprises a thin film orthin sheet of paper, metallic foil, and/or a plastic material. In someexamples, the second flexible substrate comprises a metallic foil or ametallized substrate. In some examples, the second flexible substratecomprises an aluminium foil. In some example, the second flexiblesubstrate comprises a thin film of a plastic material, for example,polyethylene (PE), linear low density polyethylene (LLDPE), low densitypolyethylene (LDPE), medium density polyethylene (MDPE), high densitypolyethylene (HDPE), polypropylene (PP), cast (cPP) or axially orientedpolypropylene (BOPP), oriented polyamide (OPA). In some examples, thesecond flexible substrate comprises a plurality of layers of film of aplastic material, such as a combination of films selected from PE,LLDPE, PP, BOPP, OPA, Al, metalized BOPP, metalized PET, laminatedtogether.

In some examples, the second flexible substrate comprises a metallizedpaper in the form of a paper substrate coated on one surface with alayer of metal, for example aluminium.

In some examples, the second flexible substrate comprises a metallizedplastic film in the form of a polymer substrate coated on one surfacewith a layer of metal, for example aluminium. In some examples, thesecond flexible substrate comprises a metallized plastic film in theform of a metallized BOPP film, a metallized PET film, or a metallizedpolyethylene (PE) film. In some examples, the metallized PET or PE iscoated with a SiOx or AlOx layer.

In some examples, the second flexible substrate comprises a thin film ofmaterial, wherein the film is less than 250 μm in thickness, for exampleless than 90 μm in thickness, less than 80 μm in thickness, less than 70μm in thickness, less than 60 μm in thickness, less than 50 μm inthickness, less than 40 μm in thickness, less than 30 μm in thickness,less than 20 μm in thickness, less than 15 μm in thickness. In oneexample, the film of material is about 12 μm in thickness.

In some examples, the second flexible substrate comprises a thin film ofmaterial, wherein the film is greater than 12 μm in thickness, forexample greater than 15 μm in thickness, greater than 20 μm inthickness, greater than 30 μm in thickness, greater than 40 μm inthickness, greater than 50 μm in thickness, greater than 60 μm inthickness, greater than 70 μm in thickness, greater than 80 μm inthickness, greater than 90 μm in thickness. In some examples, the filmof material is about 250 μm in thickness.

In some examples, the second flexible substrate comprises a sealantlayer disposed on a surface thereof other than the surface on which thethermally activatable laminating material is applied, and thus on whichthe first flexible substrate printed with the ink composition islaminated. In some examples, the sealant layer is disposed on theinnermost surface of the flexible packaging material and serves toprovide means for sealing the flexible packaging material to itself oranother material, with the goods to be packaged inside. In someexamples, the sealant layer comprises a film of low-melting, i.e. heatsealable, thermoplastic material. Suitable thermoplastic materialsinclude those described herein in connection with the polymer resinand/or the thermally activatable laminating material and includepolymers of ethylene, or DuPont's Surlyn® ionomers. In one example, thesealant layer comprises an extrudable material.

In some examples, the sealant layer comprises a thin film of a polymer,wherein the film is less than 100 μm in thickness, for example less than90 μm in thickness, less than 80 μm in thickness, less than 70 μm inthickness, less than 60 μm in thickness, less than 50 μm in thickness,less than 40 μm in thickness, less than 30 μm in thickness, less than 20μm in thickness, less than 15 μm in thickness. In some examples, thefilm of polymer is about 5 μm in thickness.

In some examples, the sealant layer comprises a thin film of a polymer,wherein the film is greater than 5 μm in thickness, for example greaterthan 15 μm in thickness, greater than 20 μm in thickness, greater than30 μm in thickness, greater than 40 μm in thickness, greater than 50 μmin thickness, greater than 60 μm in thickness, greater than 70 μm inthickness, greater than 80 μm in thickness, greater than 90 μm inthickness. In one example, the film of polymer is about 100 μm inthickness.

Thermally Activatable Laminating Material (TALM)

The thermally activatable laminating material may also be referred to asa thermal laminating material or layer or polymer or thermallyactivatable laminating layer or polymer.

In some examples, the thermally activatable laminating materialcomprises a polymer resin, for example a thermoplastic polymer resin. Insome examples the thermally activatable laminating material comprises alow-melting polymer. The term “low-melting polymer” is to be understoodas a polymeric material which is solid at room temperature but melts ata temperature typically obtainable in a printing or laminatingapparatus.

In some examples, the thermally activatable laminating material maycomprise a low-melting polymer with a melting point of less than about200° C., for example less than about 190° C., for example less thanabout 180° C., for example less than about 170° C., for example lessthan about 160° C., for example less than about 150° C., for exampleless than about 140° C., for example less than about 130° C., forexample less than about 120° C., for example less than about 110° C.,for example less than about 100° C., for example less than about 90° C.,for example less than about 80° C., for example about 70° C.

In some examples, the thermally activatable laminating material maycomprise a low-melting polymer with a melting point of greater thanabout 70° C., for example greater than about 80° C., for example greaterthan about 90° C., for example greater than about 100° C., for examplegreater than about 110° C., for example greater than about 120° C., forexample greater than about 130° C., for example greater than about 140°C., for example greater than about 150° C., for example greater thanabout 160° C., for example greater than about 170° C., for examplegreater than about 180° C., for example greater than about 190° C., forexample about 200° C.

By using a low-melting polymer as the thermally activatable laminatingmaterial to form the thermally activatable laminating material, itbecomes possible to extrude the thermally activatable laminatingmaterial onto the second flexible substrate to form a layered structurefor laminating to the printed substrate.

In some examples, the thermally activatable laminating materialcomprises a thin film of a polymer, wherein the film is less than 180 μmin thickness, for example less than 160 μm in thickness, for exampleless than 140 μm in thickness, for example less than 120 μm inthickness, for example less than 100 μm in thickness, for example lessthan 80 μm in thickness, for example less than 60 μm in thickness, forexample less than 50 μm in thickness, for example less than 40 μm inthickness, for example less than 30 μm in thickness, for example lessthan 20 μm in thickness, for example less than 10 μm in thickness, forexample less than 9 μm in thickness, for example less than 8 μm inthickness, for example less than 7 μm in thickness, for example lessthan 6 μm in thickness, for example less than 5 μm in thickness, forexample less than 4 μm in thickness, for example less than 3 μm inthickness. In some examples, the film of polymer is about 2 μm inthickness.

In some examples, the thermally activatable laminating materialcomprises a thin film of a polymer, wherein the film is greater than 2μm in thickness, for example greater than 3 μm in thickness, for examplegreater than 4 μm in thickness, for example greater than 5 μm inthickness, for example greater than 6 μm in thickness, for examplegreater than 7 μm in thickness, for example greater than 8 μm inthickness, for example greater than 9 μm in thickness, for examplegreater than 10 μm in thickness, for example greater than 20 μm inthickness, for example greater than 30 μm in thickness, for examplegreater than 40 μm in thickness, for example greater than 50 μm inthickness, for example greater than 60 μm in thickness, for examplegreater than 80 μm in thickness, for example greater than 100 μm inthickness, for example greater than 120 μm in thickness, for examplegreater than 140 μm in thickness, for example greater than 160 μm inthickness. In some examples, the film of polymer is about 180 μm inthickness.

In some examples, the thermally activatable laminating materialcomprises a thin film of a polymer, wherein the film has a coatingweight of less than 160 grams per square metre (gsm), for example lessthan 150 gsm, for example less than 140 gsm, for example less than 130gsm, for example less than 120 gsm, for example less than 110 gsm, forexample less than 100 gsm, for example less than 90 gsm, for exampleless than 80 gsm, for example less than 70 gsm, for example less than 60gsm, for example less than 50 gsm, for example less than 40 gsm, forexample less than 30 gsm, for example less than 20 gsm, for example lessthan 15 gsm, for example less than 10 gsm, for example less than 9 gsm,for example less than 8 gsm, for example less than 7 gsm, for exampleless than 6 gsm, for example less than 5 gsm, for example less than 4gsm, for example less than 3 gsm. In one example, the weight of the filmof polymer is about 2 gsm.

In some examples, the thermally activatable laminating materialcomprises a thin film of a polymer, wherein the film is greater than 2gsm in weight, for example greater than 3 gsm, for example greater than4 gsm, for example greater than 5 gsm, for example greater than 6 gsm,for example greater than 7 gsm, for example greater than 8 gsm, forexample greater than 9 gsm, for example greater than 10 gsm, for examplegreater than 15 gsm, for example greater than 20 gsm, for examplegreater than 30 gsm, for example greater than 40 gsm, for examplegreater than 50 gsm, for example greater than 60 gsm, for examplegreater than 70 gsm, for example greater than 80 gsm, for examplegreater than 90 gsm, for example greater than 100 gsm, for examplegreater than 110 gsm, for example greater than 120 gsm, for examplegreater than 130 gsm, for example greater than 140 gsm, for examplegreater than 150 gsm. In one example, the weight of the film of polymeris about 160 gsm.

In some examples, the thermally activatable laminating material may be apolymer selected from ethylene or propylene acrylic or methacrylic acidcopolymers; ethylene or propylene methacrylic acid copolymers; ethylenevinyl acetate copolymers; copolymers of ethylene or propylene (e.g. 80wt % to 99.9 wt %), and alkyl (e.g. C₁ to C₅) ester of methacrylic oracrylic acid (e.g. 0.1 wt % to 20.0 wt %; co-polymers of ethylene orpropylene (e.g. 80 wt % to 99.9 wt %), acrylic or methacrylic acid (e.g.0.1 wt % to 20.0 wt %) and C₁-C₅alkyl ester of methacrylic or acrylicacid (e.g. 0.1 wt % to 20.0 wt %); co-polymers of ethylene or propylene(e.g. 70 wt % to 99.9 wt %) and maleic anhydride (e.g. 0.1 wt % to 30 wt%); polyethylene; polystyrene; isotactic polypropylene (crystalline);copolymers of ethylene ethyl acrylate; polyesters; polyvinyl toluene;polyamides; styrene/butadiene copolymers; epoxu resins; acrylic resins(e.g. copolymer of acrylic or methacrylic acid and at least oneC₁-C₂₀alkyl ester of acrylic or methacrylic acid, such as methylmethacrylate (e.g. 50% to 90%)/methacrylic acid (e.g. 0 wt % to 20 wt%)/ethylhexylacrylate (e.g. 10 wt % to 50 wt %)); ethylene-acrylateterpolymers: ethylene-acrylic esters-maleic anhydride (MAH) or glycidylmethacrylate (GMA) terpolymers; ethylene-acrylic acid ionomers, urethanepolymers and combinations thereof.

The thermally activatable laminating material may comprise a polymerhaving acidic side groups. Examples of the polymer having acidic sidegroups will now be described. The polymer having acidic side groups mayhave an acidity of 50 mg KOH/g or more, in some examples an acidity of60 mg KOH/g or more, in some examples an acidity of 70 mg KOH/g or more,in some examples an acidity of 80 mg KOH/g or more, in some examples anacidity of 90 mg KOH/g or more, in some examples an acidity of 100 mgKOH/g or more, in some examples an acidity of 105 mg KOH/g or more, insome examples 110 mg KOH/g or more, in some examples 115 mg KOH/g ormore. The polymer having acidic side groups may have an acidity of 200mg KOH/g or less, in some examples 190 mg or less, in some examples 180mg or less, in some examples 170 mg or less, in some examples 160 mg orless, in some examples 150 mg or less, in some examples 140 mg or less,in some examples 130 mg KOH/g or less, in some examples 120 mg KOH/g orless. Acidity of a polymer, as measured in mg KOH/g can be measuredusing standard procedures known in the art, for example using theprocedure described in ASTM D1386.

The thermally activatable laminating material may comprise a polymer, insome examples a polymer having acidic side groups, that has a melt flowrate of less than about 70 g/10 minutes, in some examples about 60 g/10minutes or less, in some examples about 50 g/10 minutes or less, in someexamples about 40 g/10 minutes or less, in some examples 30 g/10 minutesor less, in some examples 20 g/10 minutes or less, in some examples 10g/10 minutes or less. In some examples, all polymers having acidic sidegroups and/or ester groups in the particles each individually have amelt flow rate of less than 90 g/10 minutes, 80 g/10 minutes or less, insome examples 70 g/10 minutes or less, in some examples 70 g/10 minutesor less, in some examples 60 g/10 minutes or less.

The polymer having acidic side groups can have a melt flow rate of about10 g/10 minutes to about 120 g/10 minutes, in some examples about 10g/10 minutes to about 70 g/10 minutes, in some examples about 10 g/10minutes to 40 g/10 minutes, in some examples 20 g/10 minutes to 30 g/10minutes. The polymer having acidic side groups can have a melt flow rateof, in some examples, about 50 g/10 minutes to about 120 g/10 minutes,in some examples 60 g/10 minutes to about 100 g/10 minutes. The meltflow rate can be measured using standard procedures known in the art,for example as described in ASTM D1238.

The acidic side groups may be in free acid form or may be in the form ofan anion and associated with one or more counterions, typically metalcounterions, e.g. a metal selected from the alkali metals, such aslithium, sodium and potassium, alkali earth metals, such as magnesium orcalcium, and transition metals, such as zinc. The polymer having acidicsides groups can be selected from resins such as copolymers of ethyleneand an ethylenically unsaturated acid of either acrylic acid ormethacrylic acid; and ionomers thereof, such as methacrylic acid andethylene-acrylic or methacrylic acid copolymers which are at leastpartially neutralized with metal ions (e.g. Zn, Na, Li) such as Surlyn®ionomers. The polymer comprising acidic side groups can be a copolymerof ethylene and an ethylenically unsaturated acid of either acrylic ormethacrylic acid, where the ethylenically unsaturated acid of eitheracrylic or methacrylic acid constitute from 5 wt % to about 25 wt % ofthe co-polymer, in some examples from 10 wt % to about 20 wt % of theco-polymer.

The thermally activatable laminating material may comprise two differentpolymers having acidic side groups. The two polymers having acidic sidegroups may have different acidities, which may fall within the rangesmentioned above. The resin may comprise a first polymer having acidicside groups that has an acidity of from 10 mg KOH/g to 110 mg KOH/g, insome examples 20 mg KOH/g to 110 mg KOH/g, in some examples 30 mg KOH/gto 110 mg KOH/g, in some examples 50 mg KOH/g to 110 mg KOH/g, and asecond polymer having acidic side groups that has an acidity of 110 mgKOH/g to 130 mg KOH/g.

The thermally activatable laminating material may comprise two differentpolymers having acidic side groups: a first polymer having acidic sidegroups that has a melt flow rate of about 10 g/10 minutes to about 50g/10 minutes and an acidity of from 10 mg KOH/g to 110 mg KOH/g, in someexamples 20 mg KOH/g to 110 mg KOH/g, in some examples 30 mg KOH/g to110 mg KOH/g, in some examples 50 mg KOH/g to 110 mg KOH/g, and a secondpolymer having acidic side groups that has a melt flow rate of about 50g/10 minutes to about 120 g/10 minutes and an acidity of 110 mg KOH/g to130 mg KOH/g. The first and second polymers may be absent of estergroups. The ratio of the first polymer having acidic side groups to thesecond polymer having acidic side groups can be from about 10:1 to about2:1. The ratio can be from about 6:1 to about 3:1, in some examplesabout 4:1.

The thermally activatable laminating material may comprise a polymerhaving a melt viscosity of 15000 poise or less, in some examples a meltviscosity of 10000 poise or less, in some examples 1000 poise or less,in some examples 100 poise or less, in some examples 50 poise or less,in some examples 10 poise or less; said polymer may be a polymer havingacidic side groups as described herein. The resin may comprise a firstpolymer having a melt viscosity of 15000 poise or more, in some examples20000 poise or more, in some examples 50000 poise or more, in someexamples 70000 poise or more; and in some examples, the resin maycomprise a second polymer having a melt viscosity less than the firstpolymer, in some examples a melt viscosity of 15000 poise or less, insome examples a melt viscosity of 10000 poise or less, in some examples1000 poise or less, in some examples 100 poise or less, in some examples50 poise or less, in some examples 10 poise or less. The resin maycomprise a first polymer having a melt viscosity of more than 60000poise, in some examples from 60000 poise to 100000 poise, in someexamples from 65000 poise to 85000 poise; a second polymer having a meltviscosity of from 15000 poise to 40000 poise, in some examples 20000poise to 30000 poise, and a third polymer having a melt viscosity of15000 poise or less, in some examples a melt viscosity of 10000 poise orless, in some examples 1000 poise or less, in some examples 100 poise orless, in some examples 50 poise or less, in some examples 10 poise orless; an example of the first polymer is Nucrel® 960 (from DuPont), andexample of the second polymer is Nucrel® 699 (from DuPont), and anexample of the third polymer is A-C® 5120 or A-C® 5180 (from Honeywell).The first, second and third polymers may be polymers having acidic sidegroups as described herein. The melt viscosity can be measured using arheometer, e.g. a commercially available AR-2000 Rheometer from ThermalAnalysis Instruments, using the geometry of: 25 mm steel plate-standardsteel parallel plate, and finding the plate over plate rheometryisotherm at 120° C., 0.01 Hz shear rate.

If the thermally activatable laminating material comprises a single typeof polymer, the polymer may have a melt viscosity of 6000 poise or more,in some examples a melt viscosity of 8000 poise or more, in someexamples a melt viscosity of 10000 poise or more, in some examples amelt viscosity of 12000 poise or more. If the thermally activatablelaminating material comprises a plurality of polymers all the polymersmay together form a mixture that has a melt viscosity of 6000 poise ormore, in some examples a melt viscosity of 8000 poise or more, in someexamples a melt viscosity of 10000 poise or more, in some examples amelt viscosity of 12000 poise or more. Melt viscosity can be measuredusing standard techniques. The melt viscosity can be measured using arheometer, e.g. a commercially available AR-2000 Rheometer from ThermalAnalysis Instruments, using the geometry of: 25 mm steel plate-standardsteel parallel plate, and finding the plate over plate rheometryisotherm at 120° C., 0.01 Hz shear rate.

The thermally activatable laminating material may comprise two differentpolymers having acidic side groups that are selected from co-polymers ofethylene and an ethylenically unsaturated acid of either acrylic acid ormethacrylic acid; or ionomers thereof, such as methacrylic acid andethylene-acrylic or methacrylic acid co-polymers which are at leastpartially neutralized with metal ions (e.g. Zn, Na, Li) such as Surlyn®ionomers. The thermally activatable laminating material may comprise (i)a first polymer that is a copolymer of ethylene and an ethylenicallyunsaturated acid of either acrylic acid and methacrylic acid, whereinthe ethylenically unsaturated acid of either acrylic or methacrylic acidconstitutes from 8 wt % to about 16 wt % of the copolymer, in someexamples 10 wt % to 16 wt % of the copolymer; and (ii) a second polymerthat is a copolymer of ethylene and an ethylenically unsaturated acid ofeither acrylic acid and methacrylic acid, wherein the ethylenicallyunsaturated acid of either acrylic or methacrylic acid constitutes from12 wt % to about 30 wt % of the copolymer, in some examples from 14 wt %to about 20 wt % of the co-polymer, in some examples from 16 wt % toabout 20 wt % of the copolymer in some examples from 17 wt % to 19 wt %of the copolymer.

The thermally activatable laminating material may comprise a polymerhaving acidic side groups, as described above (which may be free ofester side groups), and a polymer having ester side groups. The polymerhaving ester side groups may be a thermoplastic polymer. The polymerhaving ester side groups may further comprise acidic side groups. Thepolymer having ester side groups may be a copolymer of a monomer havingester side groups and a monomer having acidic side groups. The polymermay be a copolymer of a monomer having ester side groups, a monomerhaving acidic side groups, and a monomer absent of any acidic and esterside groups. The monomer having ester side groups may be a monomerselected from esterified acrylic acid or esterified methacrylic acid.The monomer having acidic side groups may be a monomer selected fromacrylic or methacrylic acid. The monomer absent of any acidic and esterside groups may be an alkylene monomer, including, but not limited to,ethylene or propylene. The esterified acrylic acid or esterifiedmethacrylic acid may, respectively, be an alkyl ester of acrylic acid oran alkyl ester of methacrylic acid. The alkyl group in the alkyl esterof acrylic or methacrylic acid may be an alkyl group having 1 to 30carbons, in some examples 1 to 20 carbons, in some examples 1 to 10carbons, in some examples 1 to 5 carbons; in some examples selected frommethyl, ethyl, iso-propyl, n-propyl, t-butyl, iso-butyl, n-butyl andpentyl.

The polymer having ester side groups may be a copolymer of a firstmonomer having ester side groups, a second monomer having acidic sidegroups and a third monomer which is an alkylene monomer absent of anyacidic and ester side groups. The polymer having ester side groups maybe a copolymer of (i) a first monomer having ester side groups selectedfrom esterified acrylic acid or esterified methacrylic acid, in someexamples an alkyl ester of acrylic or methacrylic acid, (ii) a secondmonomer having acidic side groups selected from acrylic or methacrylicacid and (iii) a third monomer which is an alkylene monomer selectedfrom ethylene and propylene. The first monomer may constitute 1% to 50%by weight of the copolymer, in some examples 5% to 40% by weight, insome examples 5% to 20% by weight of the copolymer, in some examples 5%to 15% by weight of the co-polymer. The second monomer may constitute 1%to 50% by weight of the co-polymer, in some examples 5% to 40% by weightof the co-polymer, in some examples 5% to 20% by weight of theco-polymer, in some examples 5% to 15% by weight of the co-polymer. Thefirst monomer can constitute 5% to 40% by weight of the co-polymer, thesecond monomer constitutes 5% to 40% by weight of the co-polymer, andwith the third monomer constituting the remaining weight of theco-polymer. In some examples, the first monomer constitutes 5% to 15% byweight of the co-polymer, the second monomer constitutes 5% to 15% byweight of the co-polymer, with the third monomer constituting theremaining weight of the co-polymer. In some examples, the first monomerconstitutes 8% to 12% by weight of the co-polymer, the second monomerconstitutes 8% to 12% by weight of the co-polymer, with the thirdmonomer constituting the remaining weight of the co-polymer. In someexamples, the first monomer constitutes about 10% by weight of theco-polymer, the second monomer constitutes about 10% by weight of theco-polymer, and with the third monomer constituting the remaining weightof the co-polymer. The polymer may be selected from the Bynel® class ofmonomer, including Bynel® 2022 and Bynel® 2002, which are available fromDuPont.

The polymer having ester side groups may have an acidity of 50 mg KOH/gor more, in some examples an acidity of 60 mg KOH/g or more, in someexamples an acidity of 70 mg KOH/g or more, in some examples an acidityof 80 mg KOH/g or more. The polymer having ester side groups may have anacidity of 100 mg KOH/g or less, in some examples 90 mg KOH/g or less.The polymer having ester side groups may have an acidity of 60 mg KOH/gto 90 mg KOH/g, in some examples 70 mg KOH/g to 80 mg KOH/g.

The polymer having ester side groups may have a melt flow rate of about10 g/10 minutes to about 120 g/10 minutes, in some examples about 10g/10 minutes to about 50 g/10 minutes, in some examples about 20 g/10minutes to about 40 g/10 minutes, in some examples about 25 g/10 minutesto about 35 g/10 minutes.

The polymer, polymers, copolymer or copolymers of the thermallyactivatable laminating material can in some examples be selected fromthe Nucrel® family of polymers (e.g. Nucrel® 403, Nucrel® 407, Nucrel®609HS, Nucrel® 908HS, Nucrel® 1202HC, Nucrel® 30707, Nucrel® 1214,Nucrel® 903, Nucrel® 3990, Nucrel® 910, Nucrel® 925, Nucrel® 699,Nucrel® 599, Nucrel® 960, Nucrel® RX 76, Nucrel® 2806, Bynel® 2002,Bynel® 2014, Bynel® 2020 and Bynel® 2022 (sold by DuPont)), the ACfamily of polymers (e.g. A-C® 5120, A-C® 5180, A-C® 540, A-C® 580 (soldby Honeywell)), the AClyn® family of polymers (e.g. Aclyn® 201, Aclyn®246, Aclyn® 285 and Aclyn® 295), the Lotader® family of polymers (e.g.Lotader® 2210, Lotader® 3430 and Lotader® 8200 (sold by Arkema)), theLotryl® family of polymers (e.g. Lotryl® 24MA02, 29MA03 and 17BA07 (soldby Arkema)), the Escor family of polymers (e.g. Escor 5020 7.5% (sold byExxon Mobil), the Tafmer™ family of polymers (e.g. Tafmer™ MA9015 (soldby Mitsui)) and the Surlyn® family of polymers (e.g. Surlyn® 1652 (soldby DuPont)).

Process for Preparing the Flexible Packaging Material

Described herein is a process for preparing a flexible packagingmaterial comprising:

-   -   providing a first flexible substrate coated with a primer        comprising poly(acrylic acid) and/or poly(methacrylic acid);    -   printing a liquid electrophotographic printing ink composition        onto the surface of the first flexible substrate;    -   extruding a thermally activatable laminating material onto a        surface of a second flexible substrate; and    -   contacting, under conditions of temperature of at least 50° C.,        the surface of the second flexible substrate on which the        thermally activatable laminating material is deposited with the        surface of the first flexible substrate printed with the liquid        electrophotographic printing ink composition.

The process described herein is depicted generally in FIG. 1, in whichthe following reference numerals are used to identify the featuresindicated: reference numeral “1” denotes a second flexible substrate;reference numeral “2” denotes a thermally activatable laminatingmaterial; reference numeral “3” denotes a first flexible substrate;reference “4” denotes a primer comprising poly(acrylic acid) and/orpoly(methacrylic acid); reference numeral “5” denotes an ink compositionand reference numeral “6” denotes a flexible packaging material.

FIG. 1 depicts a process in which a second flexible substrate 1 iscoated with a thermally activatable laminating material 2, in adeposition process. The thermally activatable laminating material 2 isthen contacted with a first surface of a first flexible substrate 3comprising a primer comprising poly(acrylic acid) and/orpoly(methacrylic acid) 4 and an ink composition 5 in a thermallaminating step to form a flexible packaging material 6. Each step ofthe process will be described in more detail below.

In some examples, a process for preparing a flexible packaging materialcomprises a step of printing an ink composition onto a first surface ofa first flexible substrate coated with a primer comprising poly(acrylicacid) and/or poly(methacrylic acid), or providing a first flexiblesubstrate comprising a first surface coated with a primer comprisingpoly(acrylic acid) and/or poly(methacrylic acid) and an ink compositionprinted onto the first surface of the first flexible substrate. In someexamples, the first flexible substrate is a first flexible substrate asdescribed herein previously. In some examples, the ink composition usedin the process is an ink composition as described herein previously. Theink composition may be printed onto the first surface of the firstflexible substrate in a conventional electrophotographic orelectrostatic printing process using a conventional electrophotographicor electrostatic printing apparatus. Examples of suitableelectrophotographic or electrostatic printing equipment are the HPIndigo digital presses.

In some examples, the first flexible substrate comprises a transparentmaterial and the ink composition is printed onto the first surface ofthe first flexible substrate thereof in a reverse printing process suchthat the printed image or information appears correct when viewedthrough the flexible substrate. By using the reverse printing process,and thermally laminating the printed surface of the first flexiblesubstrate to the second flexible substrate (as described below), theprinted image or information is viewed correctly in the final productand is protected from damage by the first flexible substrate which formsthe outermost layer of the packaging material. The first flexiblesubstrate comprising the printed image or information can be wound ontoa roll or spool and stored until the laminating step is carried out, ifrequired.

In some examples, a process for preparing a flexible packaging materialcomprises a step of extruding a thermally activatable laminatingmaterial onto a first surface of a first flexible substrate coated witha primer comprising poly(acrylic acid) and/or poly(methacrylic acid) toform a thermally activatable laminating material disposed on the firstsurface of the first flexible substrate, or providing a second flexiblesubstrate with a thermally activatable laminating material extruded ontothe first surface of the second flexible substrate. The term“extrusion”, as used herein, is to be understood as meaning melting thethermally activatable laminating material and passing it through anextrusion die onto a base layer material in such a manner that thematerials form a structure, for example a film, of defined layers ofdifferent materials. Such processes and machinery for producing suchmaterials are known in the art.

In some examples, the second flexible substrate is a second flexiblesubstrate as described previously. In some examples, the base materialor the base layer is a preformed base layer. In some examples, thethermally activatable laminating material is a thermally activatablelaminating material as described previously.

The step of extrusion of the thermally activatable laminating substrateonto the surface of the second flexible substrate to form a layeredstructure can be performed using any apparatus suited to extrusionprocesses in which one material is extruded onto a base layer to formlayered films. Such machinery is known in the art. In the example inwhich the thermally activatable laminating material comprises a blend ofmaterials, each component of the thermally activatable laminatingmaterial may be melt blended and then extruded to form pellets ofblended thermally activatable laminating material. These pellets maythen be used in the extrusion step to form a thermally activatablelaminating material disposed on the second flexible substrate. In analternative example, the thermally activatable laminating material maycomprise a blend of materials, the blend being achieved by dry blendingpellets of each component and adding the mixture of pellets to theextruding machine used to extrude the thermally activatable laminatingmaterial and form the layered structure of a thermally activatablelaminating material disposed on the second flexible substrate. In oneexample, the process may further comprise deposition of a sealantmaterial to form a sealant layer disposed on a surface of the secondflexible substrate other than the surface on which the thermallyactivatable laminating material is disposed. The material used to formthe sealant layer may be as described previously. The step of depositingthe sealant material onto the second flexible substrate may occur beforeor after the step of extruding the thermally activatable laminatingmaterial. The step of depositing the sealant layer may take place by anysuitable process, for example, extrusion coating, flexo coating, gravureor screen printing. Thus, in this example, the steps of extruding athermally activatable laminating material and depositing a sealant layerresult in a multi-layer or trilayer material being obtained in which thesecond flexible substrate has a thermally activatable laminatingmaterial disposed on a first surface and a sealant layer disposed on asurface other than the first surface. In one example, the secondflexible substrate and sealant layer are pre-formed as a functionalsubstrate.

In some examples, a process for preparing a flexible packaging materialcomprises a step of contacting under conditions of temperature greateror equal to 50° C. the thermally activatable laminating material withthe first surface of the first flexible substrate coated with a primercomprising poly(acrylic acid) and/or poly(methacrylic acid) andcomprising the ink composition. This step may be referred to as alaminating step or a thermal laminating step. The result of this step isa thermally laminated flexible packaging material, which, as mentionedpreviously, comprises the first flexible substrate as the intendedoutermost layer of the packaging in use, thus protecting from damage theprinted image or information formed by the ink composition. In someexamples, the first flexible substrate coated with a primer comprisingpoly(acrylic acid) and/or poly(methacrylic acid) and comprising theprinted image or information is brought into a particular alignment withthe second flexible substrate comprising the thermally activatablelaminating material before being subjected to the thermal laminatingstep.

In one example, the step of contacting under conditions of temperaturegreater or equal to 50° C. the thermally activatable laminating materialwith the first surface of the first flexible substrate comprising theprinted ink composition produces the flexible packaging material whichis ready for use immediately upon cooling to room temperature, even whenusing thickener materials. Thus, in some examples, the processes forpreparing a flexible packaging material described herein require noadditional curing time, or stated differently, zero curing time. Thepresently described processes are therefore advantageous over existingmethods for producing flexible packaging materials containing LEPprinted images or information in which laminating adhesives are used.Such laminating adhesives, both “solvent-based” and “solvent-free”adhesives require curing times of at least several days, thus removingthe advantage of speed that digital printing can offer. The presentlydescribed processes are also advantageous over existing methods forproducing flexible packaging materials such as zero cure time pouchesfor sterilization, hot fill, pasteurization and retort.

In some examples, a process for preparing a flexible packaging materialcomprises a step of contacting under conditions of temperature greateror equal to 50° C. the thermally activatable laminating material of thesecond flexible substrate with the first surface of the first flexiblesubstrate and comprising the printed ink composition, and a step ofcooling the resulted material to room temperature, thereby obtaining aready-to-use flexible packaging material.

In some examples, the laminating step may be carried out on anyapparatus suited for performing such a task. Suitable laminatingequipment for preparing flexible packaging comprising laminatedmaterials is known in the art. The laminating apparatus on which thethermal laminating step may be carried out may comprise pre-heatingrolls, heating or nip rolls, and chill or cooling rolls through whichthe thermally laminated multilayer material passes, to further speed upthe cooling process. The laminating step carried out on the nip roll maybe carried out at a temperature greater or equal to 50° C. to partiallymelt the thermally activatable laminating material and/or the polymerresin of the ink composition printed on the first flexible substrate atthe laminating nip, and thereby creating a bond between the materials.

In some examples, the temperature for the laminating nip or step may beless than about 180° C., for example less than about 170° C., forexample less than about 160° C., for example less than about 150° C.,for example less than about 140° C., for example less than about 130°C., for example less than about 120° C., for example less than about110° C., for example less than about 100° C., for example less thanabout 90° C., for example less than about 80° C., for example less thanabout 70° C., for example less than about 60° C. In some examples, thetemperature for the laminating nip or step may be greater than about 50°C., for example greater than about 60° C., for example greater thanabout 70° C., for example greater than about 80° C., for example greaterthan about 90° C., for example greater than about 100° C., for examplegreater than about 110° C., for example greater than about 120° C., forexample greater than about 130° C., for example greater than about 140°C., for example greater than about 150° C., for example greater thanabout 160° C., for example greater than about 170° C.

In some examples, the temperature for the laminating nip is of 50-180°C. It will be understood that the temperature required for efficientthermal lamination will depend on the nature or composition of thethermally activatable laminating material and/or the polymer resin ofthe ink composition and the associated melting temperatures.

In some examples, the surface of the first flexible substrate printedwith the ink composition is contacted with the surface of the secondflexible substrate on which a thermally activatable laminating materialis disposed for a period of 100-600 ms.

In some examples, the pressure for the laminating nip or step may beless than about 10 bar, for example less than about 9 bar, for exampleless than about 8 bar, for example less than about 7 bar, for exampleless than about 6 bar, for example less than about 5 bar, for exampleless than about 4 bar, for example less than about 3 bar, for exampleabout 2 bar.

In one example, the pressure for the laminating nip or step may begreater than about 2 bar, for example greater than about 3 bar, forexample greater than about 4 bar, for example greater than about 5 bar,for example greater than about 6 bar, for example greater than about 7bar, for example greater than about 8 bar, for example greater thanabout 9 bar, for example about 10 bar. It will be understood that thepressure required for efficient thermal lamination will depend on thenature or composition of the thermally activatable laminating materialand the associated melting temperature.

EXAMPLES

The following illustrates examples of the methods and related aspectsdescribed herein. Thus, these examples should not be considered aslimitations of the present disclosure, but are merely in place to teachhow to make examples of the present disclosure. As such, arepresentative number of compositions and their method of manufactureare disclosed herein.

Preparation of the Second Flexible Substrate on which a ThermallyActivatable Laminating Material is Deposited

Polymer Resins:

Lotryl® 24MA02 is an ethylene-methyl acrylate copolymer (EMA), availablefrom Arkema. Lotryl® 29MA03 is an ethylene-methyl acrylate copolymer(EMA), available from Arkema. Lotryl® 24MA02 is an ethylene-methylacrylate copolymer (EMA), available from Arkema. Lotader® 3430 is anethylene-acrylic ester-maleic anhydride terpolymer, available fromArkema.

Tafmer® MA9015 is an acid modified polyolefin, available from Mitsui.

Second Flexible Substrate:

-   -   Al foil (7 μm) used was a commercially available material        obtained from VAW Hydro under product codes 8079AA or 1200 AA;    -   BOPA (15 μm) used was a commercially available material obtained        from Xiamen Changsu Industry, China;    -   cPP (80 μm) used was a commercially available material obtained        from Etimex, Germany;    -   cPP (70 μm) used was a commercially available material obtained        from Polifilm, Germany;    -   Polyethylene (PE) used was a commercially available material        obtained from Flexfilm, Germany;    -   Metalized BOPP (20 μm) (Met-BOPP) used was a commercially        available material obtained from Flexfilm;    -   PET (12 μm) used was a commercially available material obtained        from Polifilm;    -   PET-SiOx (12 μm) used was a commercially available material        obtained from Amcor Swiss;    -   PET-AlOx (12 μm) used was a commercially available material        obtained from Toray Japan;    -   BOPP (20 μm) used was a commercially available material obtained        from Dor Film.

Adhesive for pre-lamination of second flexible substrate: Dow Adcote811+catalyst F-9.

Lamination of materials to form the second flexible substrate:

Apparatus: UTECO MISTRAL [1260 mm width] Coating/Laminating machine

TABLE 1 Parameters for lamination of materials to form the secondflexible substrate Parameter Value Unwinder A tension (N) 6 Unwinder Btension (N) 10 Rewinder Tension (N) 23 Nip temperature (° C.) 60 Nippressure (bar) 4 Lamination speed (m/min) 40 Corona A (W) 0 Corona B (W)2000 Room temperature (° C.) 15-35 Room humidity (%) 30-80 Dr bladepressure (bar) 4 Gravure type 60-70 Oven 1 Temperature (° C.) 70 Oven 2Temperature (° C.) 85 Oven 3 Temperature (° C.) 100 Adhesive coat weight(gsm) 3.51. Upload first substrate on unwinder A2. Upload second substrate on unwinder B3. Put adhesive (ADH) in the tray4. Warm up the oven5. Operate the speed and close the coating head NIP6. Operate the corona to 2000 watt7. Reach 100 m/min speed and close the nip for lamination8. Remove a sample and measure the coat weight, reach at least 3.5 gsm9. Finish lamination and cure finished roll10. The prelaminate is ready to use for the extrusion coating step

Extrusion coating of Thermally Activatable Laminating Material (TALM):

Apparatus: Coex Extrusion laminator & Coater MODEL EXCOL1-12/35 fromDolci Extrusion SRL

The prelaminate Al (7 μm)/ADH/BOPA (15 μm)/ADH/cPP (80 μm) was loadedonto the main unwinder, and the thermally activatable laminatingmaterial was loaded into the extruder, and the apparatus operatedaccording to the parameters set out in Table 2:

TABLE 2 Parameter Value Unwinder A tension (N) 11 Unwinder B tension (N)9 Rewinder Tension (N) 28 Chill roll temperature (° C.) 60 Corona Tr (W)2000 Die temperature (° C.) 275 Die height (mm) 230 Extruder Atemperature (° C.) 270 RPM (A, B, C) 66 Die pressure (bar) 140 Nippressure (bar) 5 Pressure roll temperature (° C.) 120 Lamination speed(m/min) 240 Corona Rewinder (W) 4500

The result of the above processes is a prelaminate of thermallyactivatable laminating material as a top layer of a multilayer materialin the form TALM (10 μm)/Al (7 μm)/ADH/BOPA (15 μm)/ADH/cPP (80 μm).This laminate is further laminated to a printed first flexible substratePET/primer comprising poly(acrylic acid) and/or poly(methacrylicacid)/ink composition as described below.

All the prelaminates exemplified and tested in Table 6 were prepared andcoextruded according to the same procedure as described above.

Preparation of the First Flexible Substrate

A first flexible substrate coated with a primer comprising poly(acrylicacid) and/or poly(methacrylic acid) on a surface of the first flexiblesubstrate to which an ink composition was printed was used: the Sarafil®DP100-1G and Sarafil® DB100-1G0 products (available from Polyplex).

An image was electrostatically printed using a HP Indigo 20000 printingpress and ElectroInk® 4.5 (available from HP Indigo), a liquidelectrophotographic ink composition comprising a thermoplastic resincomprising ethylene acrylic acid, ethylene methacrylic acid copolymers,on the PET film, the image included white and non-printed areas, theprinted areas having an ink coverage of 100-350% (1.0 gsm-4.0 gsm coatweight of the thermoplastic resin on the PET film).

TABLE 3 Print substrate definitions PET BOPP Type Film Film Material PETBOPP Face-stock Transparent Transparent Gloss level Semi-matteSemi-matte Second transfer (kg) 250 250 Blanket temperature (° C.) 105105 Feed Fan (V)   8   8 PTH (° C.) Off Off Thickness (μm)  12  20

Print Procedure

1.1. Install the required substrate and measure surface energy on outerside with dyne pens1.2. Change printing machine definitions according to tables above1.3. Perform 1^(st) and 2^(nd) transfer calibrations1.4. Perform full color adjustment and measure OD values with X-Ritewith target OD values in Table 5

1.5. Print job

1.6. After printing remove roll to laminator for the next step

TABLE 4 Target OD values Y M C K W Target 0.95 ± 0.05 1.3 ± 0.05 1.3 ±0.05 1.5 ± 0.05 0.38 ± 0.05 OD values X-rite Y M C K C screen

Thermal Lamination Process

In this process the printed first flexible substrate coated with aprimer comprising poly(acrylic acid) and/or poly(methacrylic acid) isthermally laminated to the second flexible substrate on which thethermally activatable laminating material is deposited.

1. Place printed substrate in unwinder A and second substrate inunwinder B, allow laminator nip to reach the required temperature2. Operate the laminator for thermal lamination3. Complete lamination and follow sample measurements4. Final film configuration is: PET/primer comprising poly(acrylic acid)and/or poly(methacrylic acid)/INK/TALM/Al/OPA/cPP

TABLE 5 Operating parameters for thermal lamination Parameter ValueUnwinder A Tension (N) 9 Unwinder B Tension (N) 5 Rewinder Tension (N)16 Nip temperature (° C.) 140 Nip pressure (bar) 5 Lamination speed(m/min) 15 Corona A (KW) 2 Corona B (KW) 2

Results Lamination Bond Strength at Room Temperature

The laminate performance was verified at zero cure time by measuring thelamination bond strength immediately after the flexible packagingmaterial had been cooled at room temperature. Lamination bond strengthwas measured according to ASTM F0904-98R08.

The results are shown in Table 6 below.

Resistance to deep freeze at −18° C.

The resistivity of the flexible packaging material at a temperaturebelow 0° C. was also verified. The deep freeze test was done bypreparing 200×100 mm package from the laminate. The package wasmanufactured from the flexible packaging material as follows:

-   -   the package was sealed at three extremities    -   the pouch was filled with 300 mL of water at room temperature        and sealed at the fourth extremity    -   immersed in 300 mL of water at 21° C. and placed in a freezer at        −18° C. for seven days    -   the package was out to room temperature 23-28° C. for 48 hours    -   the pasteurized package put into carton box.

The package was then visually inspected for detection of:

-   -   any detachments between layers which usually would show as        “bubbles” on the surface of the package,    -   change in the colors of the printed picture taking as reference        a non-tested sample,    -   delaminations,    -   clear separation between layers,    -   leaks of fluid from the package through sealing border or/and        through the film itself    -   lamination bond strength after the deep freeze test was measured        according to ASTM F0904-98R08. The results are shown in Table 6        below.

Hot Fill Up to 99° C.

Hot fill is a sterilization process that is used for many applications.For the relevant laminates construction, hot fill test was done bypreparing 200×100 mm package from the laminate. The package wasmanufactured from the flexible packaging material as follows:

-   -   the package was sealed at three extremities    -   the pouch was filled with 300 mL of hot water at 99° C. and        sealed at the fourth extremity    -   the package was out to room temperature 23-28° C. for 24 hours    -   the hot filled package put into carton box

The package was then visually inspected for detection of:

-   -   any detachments between layers which usually would show as        “bubbles” on the surface of the package,    -   change in the colors of the printed picture taking as reference        a non-tested sample,    -   delaminations,    -   clear separation between layers,    -   leaks of fluid from the package through sealing border or/and        through the film itself lamination bond strength after the deep        freeze test was measured according to ASTM F0904-98R08. The        results are shown in Table 6 below.

Hot Fill and Pasteurization Test at 99° C.

Hot fill and pasteurization is a sterilization process that is used formany applications. For the relevant laminates construction,pasteurization test was done by preparing 200×100 mm package from thelaminate. The package was manufactured from the flexible packagingmaterial as follows:

-   -   the package was sealed at three extremities    -   the pouch was filled with 300 mL of hot water at 99° C. and        sealed at the fourth extremity    -   immersed in 5 L of boiling water at 99° C. for a period of 1        hour    -   the package was out to room temperature 23-280° C. for 24 hours    -   the pasteurized package put into carton box.

The package was then visually inspected for detection of:

-   -   any detachments between layers which usually would show as        “bubbles” on the surface of the package,    -   change in the colors of the printed picture taking as reference        a non-tested sample,    -   delaminations,    -   clear separation between layers,    -   leaks of fluid from the package through sealing border or/and        through the film itself,    -   lamination bond strength after the deep freeze test was measured        according to ASTM F0904-98R08. The results are shown in Table 6        below.

Retort Test at 121° C.

Retort is one of the most complicated flexible packaging processes sincethe whole package is heated to elevated temperature with steam and thencooled back to room temperature under pressure. Retort cannot be metwith some existing flexible packaging materials due to primers usedhaving unsuitable water resistance and lamination bond strength valuesbeing insufficient. For the relevant laminates construction, retort testwas done by preparing 200×100 mm package from the laminate. The packagewas manufactured from the flexible packaging material as follows:

-   -   the package was sealed at three extremities    -   the pouch was filed with 300 mL of hot water at 85° C. and        sealed at the fourth extremity    -   the filled pouch was placed in an autoclave (Tuttnauer Elara        9i). Next steam flows into the closed chamber, and the autoclave        was gradually heated for 30 minutes up to 121° C., with a        process of air removal from the chamber. Afterwards the        temperature remained at 121° C. for 20 minutes—the sterilization        stage.    -   the package was cooled slowly for 60 minutes, while pressure was        exceeded gradually up to 3 bar in order to balance the package        pressure during cooling. The cooling stage was stopped when the        autoclave temperature reached 85° C., and the pressure was        stabilized to atmospheric pressure so the autoclave door could        be opened.

The package was then removed from the autoclave and visually inspectedfor detection of:

-   -   any detachments between layers which usually would show as        “bubbles” on the surface of the package,    -   change in the colors of the printed picture taking as reference        a non-tested sample,    -   delaminations,    -   clear separation between layers,    -   leaks of fluid from the package through sealing border or/and        through the film itself,    -   lamination bond strength after the deep freeze test was measured        according to ASTM F0904-98R08. The results are shown in Table 6        below.

TABLE 6 Lamination bond Visual strength (N/inch) inspection Thermallyactivatable After After After After Hot fill and After after ExampleFinal laminate Thickness (μm) laminating material lamination Freeze testHot fill pasteurization retort processes 1 PET/Ink/TALM/ 12/2/10/70Lotryl ® 5.1 5.0 4.8 4.8 — Good cPP 24MA02 2 PET/Ink/TALM/ 12/2/10/80Lotryl ® 5.7 5.8 5.3 5.3 — Good PE 24MA02 3 PET/Ink/TALM/ 12/2/10/80Lotader ® 7.1 7.0 6.8 6.8 — Good PE 3430 4 PET/Ink/TALM/ 12/2/10/7/15/80Lotryl ® 5.7 5.4 5.4 5.3 5.0 Good Al/BOPA/cPP 29MA03 5 PET/Ink/TALM/12/2/10/12/15/80 Lotryl ® 5.8 5.3 5.2 5.6 5.0 Good PET-SiOx/BOPA/ 29MA03cPP 6 PET/Ink/TALM/ 12/2/10/7/15/80 Lotryl ® 5.2 5.3 5.2 5.3 5.1 GoodPET-AlOx/BOPA/ 17BA04 cPP 7 PET-AlOx/Ink/ 12/2/10/7/15/80 Lotryl ® 5.55.0 5.5 5.5 5.5 Good TALM/BOPA/cPP 17BA04 8 PET-SiOx/Ink/ 12/2/10/15/80Lotryl ® 5.7 5.6 5.7 5.3 5.4 Good TALM/BOPA/cPP 17BA04 9 BOPP/Ink/TALM/20/2/10/20 Tafmer ™ 5.0 5.0 — — — Good Met-BOPP MA9015 10 BOPP/Ink/TALM/20/2/10/20 Tafmer ™ 4.8 4.8 — — — Good BOPP MA9015 11 BOPP/Ink/TALM/20/2/10/80 Tafmer ™ 4.8 4.8 — — — Good PE MA9015

While the compositions, methods and related aspects have been describedwith reference to certain examples, those skilled in the art willappreciate that various modifications, changes, omissions, andsubstitutions can be made without departing from the spirit of thedisclosure. It is intended, therefore, that the invention be limited bythe scope of the following claims. The features of any dependent claimmay be combined with the features of any of the other dependent claimsor any and/or any of the independent claims.

1. A process for preparing a flexible packaging material comprising:providing a first flexible substrate coated with a primer comprisingpoly(acrylic acid) and/or poly(methacrylic acid); printing a liquidelectrophotographic printing ink composition onto the surface of thefirst flexible substrate; extruding a thermally activatable laminatingmaterial onto a surface of a second flexible substrate; and contacting,under conditions of temperature greater or equal to 50° C., the surfaceof the second flexible substrate on which the thermally activatablelaminating material is deposited with the surface of the first flexiblesubstrate printed with the liquid electrophotographic printing inkcomposition.
 2. A process according to claim 1, wherein the firstflexible substrate comprises biaxially oriented polyethyleneterephtalate (BOPET), biaxially oriented polypropylene (BOPP), orbiaxially oriented polyamide (BOPA) material.
 3. A process according toclaim 1, wherein the primer comprises poly(acrylic acid).
 4. A processaccording to claim 1, wherein the ink composition comprises a copolymerof an alkylene monomer and a monomer selected from acrylic acid andmethacrylic acid.
 5. A process according to claim 1, wherein the secondflexible substrate comprises a film or sheet of paper, metallic foil,and/or a plastic material.
 6. A process according to claim 1, whereinthe thermally activatable laminating material comprises a copolymer ofan alkylene monomer and a monomer selected from acrylic acid andmethacrylic acid.
 7. A process according to claim 1, further comprisinga sealant material onto the second flexible substrate to form a sealantlayer disposed on a surface of the second flexible substrate other thanthe surface on which the thermally activatable laminating material isdisposed.
 8. A process according to claim 1, wherein the surface of thefirst flexible substrate printed with the ink composition is contactedwith the surface of the second flexible substrate on which the thermallyactivatable laminating material is disposed, at a temperature of 50-180°C.
 9. A process according to claim 1, wherein the surface of the firstflexible substrate printed with the ink composition is contacted withthe surface of the second flexible substrate on which the thermallyactivatable laminating material is disposed for a period of 100-600 ms.10. A process according to claim 1, further comprising cooling thematerial obtained from the step of contacting the surface of the firstflexible substrate printed with the ink composition with the surface ofthe second flexible substrate on which the thermally activatablelaminating material is deposited, thereby producing the flexiblepackaging material.
 11. A flexible packaging material comprising: afirst flexible substrate coated with a primer comprising poly(acrylicacid) and/or poly(methacrylic acid); a printed liquidelectrophotographic printing ink composition disposed on a surface ofthe first flexible substrate; and a second flexible substrate on which athermally activatable laminating material is deposited, the surface ofthe second flexible substrate on which a thermally activatablelaminating material is deposited being thermally laminated to thesurface of the first flexible substrate printed with the inkcomposition.
 12. A flexible packaging material according to claim 11,wherein the first flexible substrate comprises biaxially orientedpolyethylene terephtalate (BOPET), biaxially oriented polypropylene(BOPP), or biaxially oriented polyamide (BOPA) material.
 13. A flexiblepackage comprising a flexible packaging material comprising: a firstflexible substrate coated with a primer comprising poly(acrylic acid)and/or poly(methacrylic acid); a printed liquid electrophotographicprinting ink composition disposed on a surface of the first flexiblesubstrate; and a second flexible substrate on which a thermallyactivatable laminating material, the surface of the second flexiblesubstrate on which a thermally activatable laminating material isdeposited being thermally laminated to the surface of the first flexiblesubstrate printed with the ink composition.
 14. A flexible packageaccording to claim 13, wherein the first flexible substrate comprisesbiaxially oriented polyethylene terephtalate (BOPET), biaxially orientedpolypropylene (BOPP), or biaxially oriented polyamide (BOPA) material.